Can't go on forever ignoring the bad apple. Players using foul language especially without any reason should be banned for a length of time. Not sure if it's against the rules to name and shame players here, I got the screenshot to prove it. Even once created a gamer name tag sending abuse to Midoki, time to serve justice
I believe I know which case you're talking about, and, given the language in this case, your delightful visitor has been given a temporary ban. Which means the rest of their guild will have to work that bit harder during the Event, as they're out of action. If they (or anyone else) continues the same pattern of behaviour, let us know. As ever, we always encourage people to report abusive behaviour, and we'll investigate and dole out punishment accordingly. We expect players to be able to enjoy the game without randoms suddenly popping into their guild and shouting abuse!