I would take that bumper sticker as a case of humor/sarcasm myself. But that's because I'm basically a goof much of the time. I doubt if the person is using it in a negative way towards gays/lesbians tho.
Think I read this on one of the threads here - but I was thinkin' this would be a good bumpersticker: Save family values, ban heterosexual marriage.
Now, back to our BBQ!!