For those more mature than me, you probably just ignore them. But last week we were at the DC United game sitting in front of a section of Columbus fans annoying the crap out of us.
They had the upper hand most of the game, but when the United finally salted away the victory, a bunch of us turned around and started taking flash of the visiting fans with our phones. Don't worry about the picture actually coming out, just make sure your flash goes off as much as possible.
Please apply this technique to Cowpie and dog murderer fans as you see fit.