I guess it really depends on the situation, or rather how the taunt is used. Of course, you can never know the persons true intents via taunts and can only make assumptions (unless they're very obvious about it). It sometimes boils down to how you view it.
For example, there's a lot of players (even me) who find it respectful to taunt before a match; however there's some who don't bother with it at all and will even take that chance to attack you. I only tend to do it if my opponent does first, otherwise I don't bother with "Taunt greetings" as again, not everyone does it. Some may consider it disrespectful to taunt after each and every KO while others deem it as unnecessary. For me, my general rule is I do not taunt period unless my opponent does it first.
Now there are people who are very obvious that they mean disrespect by taunting. I've encountered various players on For Glory who will literally taunt every chance they get, and usually they are the kind of people who like to fling insults at you after they win.
So I guess it again, boils down to how you and/or your opponent views taunting. Not everyone does it to be a total butt munch (cenors kiddies, keep it soft!) but at the same time there's some who obviously mean harm by doing it. If you wish to taunt then taunt away. If you feel like it might be taken offensively then don't do it. There's no rule that forbids you from doing it after all.
Just use your taunts wisely, or better yet don't do it unless your opponent does first. It's really up to you.