I know we all tend to side with the core family, but lets look at this from Zack's perspective. He is in love with a guy and pursuing a career where hetero is not only just the norm, any deviance could spell the end of said career. Remember, this is more than 15 years ago. Coming out in the NFL was unheard of, and coming out in college would mean no NFL. Thats a really tough place for a kid to be.
Top all that off with the guy he loves is not only out, he is proud of it. Just as Zack can't risk his career by coming out, Will would never be able to step back into the closet, assuming that would even be possible given Will's high profile life.