What white people did to his ancestors--including his parents, grandparents and even to him certainly has a role in every aspect of his life.
A lot of people had bad things happen to them when they were growing up. We don't use that to excuse bad behavior in other situations, why should race be treated differently?
We generally also don't use it to smear them when bad things are done to them. Why should race be treated differently?
I mean shit, I have 'telecommunications fraud' and 'disorderly conduct', and 'posession THC' buried somewhere in my past; sure, my record has been cleared since (hell, I've had a security clearance since!), But you can be sure as hell that if I was black and someone lynched me, you and the rest of them would be smearing me like "he had it coming, he was a criminal!"
Thankfully, though, I'm white so I don't have to worry about that.
The fact that people bring up "but he's Time Traveling Hitler so it's ok!" Doesnt apply if the shooter couldn't prove in the moment that they were assaulting time traveling Hitler. No, a mustache is not enough evidence to establish time traveling Hitler in the moment.