I won't be aggressive and in response I just give
them a polite notice that they are off topic and then "block sender" or
"killfile" so that's the last I read from them.

I would say that the best thing to do is not give anyone any notice in the
first place. I'm not slamming you, I agree with your sentiment, but
unfortunately OT'ers don't care if they're OT (hell, I admit I've done it
myself, though only once in a great while). If there's someone who's
consistently posting trash, I simply killfile them, no notice, no "I killfiled
you" posting, nothing. Just block them, because if you give them notice first
(polite or not) it just encourages them to get hostile, throw more trash into
the fray, and make things uglier all the way around.
Linus