It honestly varies.
Lot's of people try to Taunt to disrespect you, while others may do it either out of habit or because they literally bodied you. If someone ends up getting me in a good combo then finishes me off, I don't think I can get mad at a Taunt. I mean, they're allowed to do it after something like that whether they mean it as disrespect or something else. I just can't find myself to get mad in that case.
However, if someone triple taunts, taunts when it was something so simple or easy (or when I SD), teabags, whatever I tend to switch into overdrive mode. I always play seriously mind you, but when something like that happens I'm suddenly more determined to beat them. To me, some folks act so tough and cocky when they're really nothing to shrug at so I get that feeling of wanting to knock them down a peg. I'm typically really respectful too or at least attempt to be. I almost never Taunt unless they do it first, always return as Taunt at the start of the match, say "GG" if someone does it to... I honestly try to be a good sport when I can.
Sometimes though, so folks really tend to ask for it due to their arrogance.
Basically, it's a 50/50. If the player isn't really all that great I definitely tend to pay them back for it because it makes me play that much harder; however sometimes players can back up their talk and I get a little irritated and my judgement tends to get clouded.
At the same time, if they can back up their Taunts/cockiness I suppose it's nothing to get that mad over. They obviously got skill.
Doesn't really excuse the players who triple taunt and teabag players who are obviously of a lesser skill though, unless they ask for it I guess...?
