I don't have the experience yet, as we don't have openly gay members in our charge but I believe the situation also depends on where you are pledging.
For some "liberal" states, like New York or California, being gay and greek is acceptable. It will be different for some Greek houses in more "traditional" states to pledge gay.
About being gay and having big white cross pin on the chest, I don't think that matters. Hey, Christians are for everyone, and if you believe in Jesus, and you're gay, so what? Can you proudly shown both on you? Christians started from one group (race), and now, you can see every ethic groups, including whites (and gays!), believe and accept Jesus as their savior.
Personally, I encourage everybody to go Greek, gay or straight. Like everyone else mentioned, Greek is not all about sex orientation, nor religion.
Just my .2 cents
