I doubt this guy is the first homosexual to play in the majors, so that comparison makes no sense.
Well, he absolutely wouldn't be the first homosexual to play in the NFL. One of the greatest Redskins of all time, and one of the best Tight Ends ever (he really should be getting a look at the hall of fame by the senior committee at some point), Jerry Smith was a homosexual. However, Michael would be the first openly gay player to actively be drafted and/or play in the NFL while gay which is why it's a big deal.
And I don't think there'd be anything wrong at all with someone being uncomfortable about showering with him. Hell, I know guys who are uncomfortable showering with other straight guys. Making that an issue, either on one side going "We can't have them there! someone may feel uncomfortable showering with them" or going "Wow! What an ass, how dare he feel uncomfortable", is just ridiculous to me.
Now, it will probably take a strong locker room. And I do think what steeler's Safety Ryan Clark said recently is going to play into things...how does the guy handle a lockerroom. Guys make fun of guys, and football players largely are unfiltered. Clark said something along the lines of how they'll make fun of guy whose ugly, or whose fat, or whose spouse is ugly, etc because generally in the locker room it's known to all be just kind of part of the ribbing and the fun. I don't doubt the guy's going to get some ribs, especially as a rookie, that relate to his sexual orientation (just like I'm sure guys will get ribbed if they went out with a "dog" the night before. Guys joke about sex lives in gratitous fashion often). The question would be how he handles that.
However, I'd not worry too much about that. First, that's something in a general sense every NFL team does...trying to see if a guy coming in is going to be able to handle the personality of an NFL locker room. This will happen even more in light of the stuff down in Miami. Two, I can't imagine that with his teammates at Mizzu knowing this that there wasn't an off hand joke or two that he had to deal with and if he couldn't he would've had more issues there.
I really don't think the "gay" thing within the locker room is going to be as bad or as big of an issue as some people are thinking.