Sadly, the prejudice does exist. There was a young woman in a sorority at my school (not mine) who was very well liked. She'd held a few offices in her chapter, including an exec board position. She was also a closeted lesbian. Feeling that she could tell her sisters anything, she came out at a fireside. And that was *it* - a lot of her sisters stopped talking to her, she was never again elected to an office, and she was basically made pretty miserable for the rest of her college years.
My sorority never had any openly gay members, but I wouldn't have any problem whatsoever, and I certainly wouldn't vote against anyone strictly because of her sexual orientation.