Why is t-bagging so normalised?

I've just started playing a couple of days ago and i like playing killer but this game just feels so toxic. I'm already put up against pro players with insane prestiges which is hard enough while i'm trying to learn the basics but the way they act is horrible. Every time I'm hit with a pallet I get t-bagged or pointed at somehow for what? Being new and missing a shot? I don't think i'm playing toxic either, I try my hardest not to do slugging or whatever it's called but it keeps happening. Is this normal?