I accidentally deleted my comment right after writing it. I'm going to write it again.

If you killed them, their property would have passed to their heirs.

Option 1: maybe you lack the tools to stop this inheritance. Maybe your only choice is to kill those heirs.

But to do so, you must now kill children. And crucially, you must now build your movement out of members who are okay with killing children.

Your new country will be a vicious, cold, brutal place.

Option 2: you figure out some way to take control of the legal system enough to strip their heirs of their wealth without killing those heirs.

Now, you've got a tool that can be wielded to separate people from their property without killing them. Which makes the first killing (the killing of the parents) optional.

Once again, to kill those parents, you must now build your movement out of members who are okay with killing when it has become optional.

The real solution with option 1 is to gain the power to make option 2 possible. The real solution with option 2 is to align yourself with those members of your movement who believe killing should be avoided whenever killing is optional.

I think the slaveowners of the south should have been stripped of their property. I think the plantations should have been given to the slaves as reparation.

I think klansmen should have been stripped of everything they owned.

But only use bullets when they show up with pitchforks to burn down one of these plantations newly transferred into black hands. Don't go seeking out former slaveowners to kill. Just kill the ones currently trying to burn down the former plantation.

At any rate, you must make a choice between aligning yourself with people who err on the side of killing (even when it's no longer necessary), and aligning yourself with people who err on the side of sparing lives (even when it causes problems.)

You don't want to alienate the latter. You don't want to give power to the former.

Deciding whether or not to kill people is not about who deserves death: it's about choosing your allies. And you don't want your allies to be the ones erring on the side of unnecessary violence.