First, gay marriage is a misnomer. The correct term is same-sex marriage. Not everyone who is or wants to be married to a person of the same gender identifies as gay - some identify as bisexual. The term “gay marriage” is thus not only very limiting but completely wrong.
Furthermore, how is marriage between two people, regardless of gender, considered “equality,” when marriage between more than two people is not legal? There are many of us who believe in polyamory – why can’t there be legal benefits to polyamorous situations as well?
Also, some religious groups, notably FLDS and Islam, allow polygamy. Those in the FLDS church, for instance, believe polygamy is essential to their eternal salvation. Not allowing plural marriage amounts to religious discrimination.
Until polyamorous relationships can be legally recognized as marriage, there is no marriage equality. Those of you who truly believe in equality should recognize that the fight is not over.