I don't think the locker room would have any problem with it. The problem would be with the fans. I think especially opposing fans. Some of the things that are said are over the top and out of control that I can imagine what some fans would say to an openly gay player.
At least he realizes it would be fine in the locker room. But fans? Really? I remember writing about trans college basketball player Kye Allums. I asked him if he was afraid of what fans might say. "I've already heard it all," he said. After all, what's the worst a fan can yell? "Faggot?" Big deal, they've all heard it before! And fans already yell those slurs. Suddenly they're going to, what, yell them more? Big deal.
Plus, over 80% of fans say they have no problem with gay people. Even the Jets fans. But you know what fans and players and everyone else are all consistent with? Blaming everyone else for homophobia. "Oh, I'm cool with it, but those people aren't." Arians is just the latest to follow the same tired pattern.
Another consistent pattern is that people STOP using these anti-gay slurs when someone comes out. They toss it around thinking the slur has nothing to do with being gay. Once you insert said openly gay person into the mix? They stop.
Arians' football players are grown men who can handle themselves. Chances are an openly gay player would hear "faggot" less from fans than he does being in the closet. Either way, Ariens should stop blaming the fans, start winning them over, and worry about his own locker room where no doubt at least one gay athlete hasn't felt comfortable coming out.