Landon Donovan looks harmless, doesn't he? He's pretty small, and his Irish heritage makes him seem fey more than threatening.
But Landon can be a terror to opposing teams and he doesn't hesitate to take on opposing fans as well. His shushing gesture, combined with the throat slit, was definitely provocative.
Here's the thing, though. Soccer isn't golf, and I don't mind passionate interaction between fans and players, though I know some will disagree.
I remember when Cobi Jones scored in an Open Cup match versus the Minnesota Thunder, and he ran over to the traveling fans section and bowed low. It was a taunt, for sure, but I thought it was clever. Bruce McGuire (of DuNord fame) disagreed completely and thought it was low class.
Where I draw the line is at sexual taunts - grotch grabbing to me is low class.
But a challenge to the fans should be taken just as that - a challenge to not shut up, to yell and support your team even more. The Crew's one-time goalkeeper, Bill Guadette, had a finger wagging, "no, no" gesture to opposing forwards in a game, and Eric Wynalda rightly called out that it would make them want to score on him more than ever. Live by the taunt, die by it - but I still think the game is more interesting with such displays.