The only reason to get mad at someone calling you a bad leftist is if you think it might be true. People will absolutely prey on your insecurity to make themselves feel like their chronic posting habit is praxis. The solution is to not be insecure. Be humble, do honest self-critique. Don't let lonely people work out their frustrations on you. There is a difference between pipe-lining and emotional blackmail.
When someone tells you that your advocacy for oppressed groups is "annoying," fuck you is an appropriate response. That's how I'd respond to anyone saying something similar about racism or feminism.
Justify your behavior all you want, you weren't being a hero to anyone but yourself.
Disengaging.