There's a difference in understanding and supporting, or considering something morally correct.
As another example: I understand why some folks get sucked into gangs. If someone grows up in a crumbling school system, falls through the holes in whatever is left of a social safety net, has no proper familial support, and sees nothing but violence and economic despair day-to-day, joining a gang suddenly becomes a viable path to prosperity. Exceedingly dangerous, but this hypothetical teen can look around and see they're likely to have a shit future regardless, so why not take that chance, right?
So this isn't me saying that I support gang violence, but I can understand why it happens. Which is why my politics are what they are: we don't need to just beat the shit out of gang members in the streets, but give folks support so they don't feel like joining a gang is the only way to survive.
The other poster is (I think) making a similar kind of argument. What the fuck else is some kid in that situation going to grow up to be? Some folks will make it out alright, sure: but on the whole it's a recipe for despair, which often leads to horrific acts. It doesn't make the acts right, but we can understand a little more about the why.
Do you get mad at geologists for explaining why volcanoes erupt and kill people?