These are competing questions because a lot of times, you can ask them about two different sides of a situation. Though usually not at the same time. For example: you might read the Bible and wonder, "Why didn't God rescue the Israelites from slavery sooner? Why'd he let it go on for 400 years?"
Then you might read about the exodus and ask, "Why did God allow (or cause!) such bad things to happen against the Egyptians? Doesn't he care about all the mothers and fathers who were suddenly bereft of their firstborn sons?"
The fact that we ask questions like these more often of the Old Testament than of the New is telling. The OT covers a lot more timeline than the NT does. It's important to keep in perspective how much time is passing and that there are many things that weren't written down and many stories that weren't told. The Bible can't tell the whole of human history, individual by individual; it'd be too long to read.
I have came across some interesting verses in my journey of reading the Bible in a year that throw light on the questionable justice displayed throughout the OT. Take Genesis 15:16, where God is telling Abraham what's going to happen to his descendants. "After four generations your descendants will return here to this land, the sins of the Amorites do not yet warrant their destruction."
This is an interesting verse. God has promised the land to Abraham's progeny, but he says, "not yet; the people there haven't sinned so much yet that they deserve to be killed and kicked out. I'm still giving them a chance to turn to me and be in relationship with me."
God knows the Amorites aren't going to turn to him. That's why he's promised the land to Abraham. But *if* they were to do so, my bet is he wouldn't bring the Israelites stomping into their land generations later. He knows they won't; he knows they're going to keep doing more and more atrocities. They're going to enslave people, and slaughter their children as sacrifices. But he's giving them a chance. He's a God who both knows the future and still gives us a chance. He acts both in time and out of time.
And here's the thing; the Israelites eventually did go down and defeat the Amorites. And we say, "War? Killing? Really, God?" But we have to remember that this was an entire people and culture whose value system involved taking the most beautiful and smart children and killing them brutally in front of everyone. It also involved finding attractive young girls and boys and raising them as temple prostitutes, available to have sex to anyone who was willing to pay some money "to the gods."
There were atrocities going on, and this was how justice was brought in that day. It is the justice of our day, too. In some ways, it has to be. Hitler may be the one we point to for World War II, but he wasn't the only one doing terrible things to people. There were many, many people who needed to be brought to justice, and no matter what Daniel Craig makes it look like, you can't always send in one man to kill the one person who's guilty. Usually it's not that simple; many people have gotten their hands dirty now, and cutting off the head doesn't guarantee you've freed the victims from slavery. A lot of times you'll just find you're fighting a worm or a lizard; it loses some pieces but keeps going and grows them back.
I'm not saying war is good, or that I'm a proponent for it. But maybe it's a necessary evil sometimes. I'd much rather have WWII in our history than have the extermination of old, handicapped, and Jewish people still going on. (Tweet this.) Sometimes war just might be the way to bring justice.
When the Israelites fought and defeated the Amorites years later, after the Amorites had been given chance after chance to do better and had just gotten worse, God used that battle to bring justice to those who had been oppressed and martyred at the Amorites' hands. When it says "they killed everyone," I often wonder what that means. Were there people whom God had rescued and who had run away to the mountains? It's hard to believe that in an entire nation *NO ONE* secretly worshiped a different god, a good god they had heard about... Did God sneak away some who had held onto him and trusted him? Or, if there were any, did God perhaps allow them to die too, as a mercy, and join him in paradise rather than live the rest of their lives with the evil they had seen?
I don't know. I don't know what would be 'right,' or what happened in all the little details. The Bible is more concerned with painting a picture of a God who would go to the ends of the earth and back to save his children from any oppression. That is the kind of person you can trust to have your back. When it comes to the questions like this that can't be answered with any proof, I lean on what I know. It's wise to assume that since God is good and did all of those loving things, he did the right and good and loving thing in this situation, too.
Maybe the Israelites conquering the Amorites was a good thing. It brought justice to a land that needed it. But why did God take so long? If it was a good thing, why did he wait? There were people being killed and raped and persecuted and enslaved. Why didn't he stop it sooner?
I'm still learning about justice, but I'll take a guess. I'm going to guess that in little ways, close up and personal, God *WAS* dealing on an individual basis with the people who committed those acts. I'm going to guess that each person got choices, and as someone continued to make bad choices, things got worse and worse for them. The thing about God is that he doesn't just toss you away if you mess up once. Or twice, even. It takes a long time. I don't know where the line is drawn; it says that God sees through the heart. I think he can tell when you've decided, not just once, but for always, that you're going to take this evil path over that good one. And I think that's when God says, "so be it." Scary words to hear from God.
To get back to the original Egypt question: why did God let the Israelites be enslaved for as long as they were, and why did he have to kill the Egyptians' firstborn sons to set them free? I don't know. But I'd guess it has to do with choices, and that for 400 years God kept giving the Egyptians leaders the choice to let the Israelites go free and do a lot of other good things: in general, to follow him and take the right path. Remember, God doesn't just love the victims; he loves the perps too.
Why did God kill their oldest sons? I don't know. But maybe it has something to do with not perpetuating the evil that was obviously pervasive in this abusive and enslaving culture. Maybe in a way it was a mercy; everyone dies, and these young men and boys died before they could be turned and persuaded and began to believe that killing, beating, and enslaving is good fun.
Everyone dies eventually. But not without many choices first. Justice gets carried out on the individual level and the national level. The answer to "why" and "why not" lies in whether God is extending mercy on the perp right now and giving him the ability to change if he will but take it--or whether the perp has rejected all attempts at grace, and God is raining down justice. Only God knows.
Somehow, both the love and the justice are beautiful. Both of them are good. But I could also do with having justice extended on behalf of the 27 million who are enslaved in our world. That's what I want. But maybe God's doing something different: sending individuals like us to set the captives free, and still offering a hand of mercy to their captors through other people like us. Maybe the reason I don't see justice is because I'm looking for national, global justice, and God working it out on the individual level instead.
And maybe next time I ask, "why me?" I should realize that it's not about me. Maybe next time it feels like I'm the one sitting on a hot bed of coals, I need to look around and see the bigger picture. I might find that what feels like a few people's problem with finding a job or being able to support themselves is in fact national (or culture-level, or city-level, or state-level, or...) justice for a gross mishandling of our economy. In the midst of that justice, I have confidence that God will offer grace on the individual. In the midst of the storm, God offers us everything we need to stay afloat. And when the storm clouds break, there will be songs of joy.