I think you are a great person and a great representation of your fraternity.
People represent their GLO by wearing their letters proudly and donating their time to their organization. Personally, I don't think anyone represents their organization by whatever sex they prefer.
I wouldn't think any less of Alpha because they had a gay member and from what I've seen of your postings on GC, I would actually think more of Alpha! Sorry to hear that some people are giving you a hard time.