I actually don't get mad at thwm, but, it's my opinion..
In comp I think it's juvenile, it's clearly a lack of sportsmanship and respect.
If i get t-bag, the worst I'll do if I kill him back is saying hello and thank.. depending on the hero I use a voice line.
For dva it's "I have the feeling you're not taking me seriously", Moira "Stupidity is not a right" and so on.