This violates the 14th Amendment. As the Boston Globe found out when it tried to offer benefits to Gay couples that were living together. But not Straight couples. Why not just count Gays in the Census so we can get the true number of their population?
Because then we would also have to count chess players, auto mechanic hobbyists, back woods hikers etc and every other practicer of a chosen behavior.
The constitution does not segregate people by behavior. Only by age and sex.