Apparantly there is a word for this. It's Biphobia.
http://en.wikipedia.org/wiki/Biphobia
"Biphobia is the fear of, discrimination against, or hatred of
bisexuals. It need not include
homophobia or
heterophobia, because there are
stereotypes that are specific to bisexuals."
In other words, they are just a bunch of Jacobs, with their arrogant "homo-superior" "hetero-superior" attitude.
There are few things that I would KO someone in public for, and I think this is definately one of those things.