Should you be just a little more ambiguous about your commitment to heterosexuality (if indeed there is one)? After all, leaving it unclear can make life easier for gays. Making a point of announcing your mainstream orientation makes it hard for others to leave their preferences unspoken.
Or does it work the other way around? Perhaps we need openly gay friends and acquaintances to make society more tolerant. It is inducing people to come out of the closet which brings the positive externality. Positive declarations of heterosexuality ("My wife is very fond of Alex…") should then be encouraged.
Are you interested in "tipping" issues, and the social construction of norms? Read the new, excellent, and surprisingly analytical Straightforward: How to Mobilize Heterosexual Support for Gay Rights, by Ian Ayres and Jennifer Gerarda Brown.