Taunting is a legit part of play. It may not have phased Mr. 5 year war vet here, but perhaps a lesser player would be angered because they'd think "oh it was a 5v1 it wasn't fair I'll show him next time" causing them to tunnel vision and not focus on the healers.

For people being taunted, just ignore it and return. For people on the taunting side, there is no shame in it. It might just squeeze out a few more points for your alliance if you get a hot-headed player.