I think I'm usually too scared to defend myself non-politely. From my real life experience, most people are selfish moron jerks and when you are mean to them they will try to punish you for it. Either directly or secretly. And since it's illegal to hardcore fuck them up for behaving like disgusting piece of shit cunts... well... what am I supposed to do? I have no interest in getting sabotaged by everyone on a daily basis just because I told them how shitty they behave. You'd be surprised how crafty people are when it comes to hurtin someone. So in the end I usually let other people shit at me too much until I will get too fed up with it and explode. It's probably a miracle I didn't kill as many people as I can and them myself yet. I know it's bad way to go about it but I don't think I have the willpower to change it.
On the internet it's of course a bit different but I already had a "fan" psycho who spammed me in my DMs with bullshit and then told me he will remember I was mean to him when I refused to spend more time talking to him about his shit.
But in my nature I like talking to other people and helping them, even on the internet, especially since I don't really have anyone to talk to in real life, which is why I tend to respond to people talking about me or my work.
But I'm not gonna lie, when I remember most people are probably disgusting despicable beings who only care about themselves, it starts to get real hard to care about anyone.