Gotta disagree RDM. Umpires do and should "respond to fans", many times with a threat to "Boot" if the fan doesn't comply. Be careful, your response sounds very much like PabloSanchez( #1 Homer). I don't think I can handle another Pablo!
Horns of any kind don't belong at a ball park. I've sat and watched & heard a group of fans ( I won't name the HS) sit in the beds of their pickup trucks and shout racial remarks to our CF. The practice is a "tradition" that must be stopped by the man that "controls" the game, Mr. Umpire. Totally unacceptable behavior.