You don't have to be gay, or bi. You don't have to know someone who is gay or bi.
You just have to think gay people are people. That they're human beings with feelings. That no one should be harrassed to death. That no one should be beaten or molested because of who they are attracted to or love. That no child or young adult should feel such a sense of self-loathing that he or she should take their own life.
Stand up against cyber-bullying of gays.
Stand up against people beating, raping and killing gay or transgendered people.
Stand up against people speaking about gays as if they are somehow lesser humans that you or me. (New Yorkers stand up against Carl Paladino!)