The only reason I might not do this is because the Holocaust was a major historical event, and stopping it from happening would therefore seriously mess up original time. Would time end up being better after that? I don’t know.
Other than that, oh yeah. Getting down to the actual shooting him part would be difficult in the moment, but I could do it.
I wouldn’t stop it. There’s a reason God allowed it to happen. Think about it, if we shot Hitler and prevented him from starting the Holocaust, another dictator could rise up and wreak worse havoc. I think I’ll trust God on the history.