Unfortunately it's still very common for people to see any affection between men as a gay thing. All jokes aside, it really is a damaging thing to tell boys that having friendships or showing physical affection towards each other is wrong. It's what leads to homophobia and adult-male depression. But for real, it's also really funny to call your friend gay after he gives you a hug. It's just one of those things that's wrong but feels so right. Maybe one day we'll evolve past it.
Hopefully that sets the scene for why this photo is funny. Right in the middle of these two teammates embracing from a hard fought game, we see an unintentional caption in the background via the other team's jersey name. He's over there saying, "you two are gay," and of course they respond with, "No, you're gay."