The primary reaction to this isn't 'I hate you because you're gay', it's 'I don't really care, do whatever you want' or 'Good for you, why is this news'. Most people simply don't care. Say what you will about tolerance, but there are few things more irritating than constant coverage of someone solely because they aren't straight. It's annoying to see this in place of real news, and it places people's sexual preferences above their actual merit. If being gay is normal, let's treat it as normally as we would treat straight people.
And I would say gay marriage would be more popular in more states if people who opposed it weren't constantly being berated or compared to actual bigots in Westboro or Iran. It doesn't help people join your cause when you judge them based on one issue - be it the pros or antis. If everyone focused more on ending the severe sexual and religious oppression discrimination in the Middle East (something I think most people on either side of anything would agree with), I think we'd get a lot more progress on general freedom than anything else... if only because it'd be reinforcing that you aren't a bad person just because you are gay, or you aren't a bad person just because you disagree with gay marriage. There are good people on both sides.
Because it is big news, that's why it is being covered. It's probably the most important story regarding the NFL because of the social prominence. Michael Sam coming out will give the public an insight as to just how homophobic the NFL still is. If he falls way short of where he should be drafted, and there aren't any primary concerns like injury, the collective league will be under scrutiny, possibly changing the entire locker room culture.