In the case of the SS, ideological alignment was kinda a prereq. The SS was specifically about the "racial policy" of Nazi Germany. It would be impossible to be permitted into the SS without being aware of those policies, and agreeing to enforce them. We're all memers of the SS specifically aware of the death camps? Maybe not, but they were certainly in the camp of "there exist unpure races which pose a danger merely by being permitted to exist".

Again, I draw a stark contrast to the regular military. Maybe they were bought into the idea, maybe they were not, it wasn't really part of their duties to enforce racial policy.

So, would he have known? Maybe not when he applied, but certainly he would have been aware before he was admitted. Enforcing racial policy was literally the explicit job of the specifically the SS.

Anyways, I agree that it's appropriate to give historical actors the benefits of attempting to morally evaluate their decisions within the context that they were made in.

At the same time, I think it's important to do the legwork to attempt to understand what that context was.

I can't speak to the specific reasons a specific man chose to join the SS, but I can speak to the fact that the SS was specifically associated with the duty of enforcing racial policy, and the regular German army was not. I'd need to hear an explanation of why he chose the SS as opposed to the regular German army if his rationale was simply that he wanted to fight Russia.