Its your right to ban friendlying on servers you administer if you so choose, but to suggest that the sole intent is to piss other people off is just plain wrong. The reason people will often attempt friendlying on hightower is because we were already there because we like that map. Then someone starts congaing and we join in for a few minutes. Then we go back to playing normally. Nobody is trying to piss anyone off and the reason we don't all go to trade/idle for our spontaneous brief conga parties is self evident.
When someone wants to friendly... it sandpits other people, while some people still want to play the game. This causes things like rage, vote abuse as well as a lose-lose situation with friendliers complaining about getting killed, and other people complaining about friendliers.
TF2 is a SHOOTER. The idea is to kill people... not doing so is just going against what the game's purpose is.
An aside also is that Congas have lasted HOURS on end in the past. Anyone tries to break this?
Vote abuse.
The only way to fix things like this is for admins to clean up the mess.