First, if you haven't already done so, download that live barn footage of him not wearing a mask. Maybe download a bunch of footage. You might need it. In fact, why not show that to the owner of the rink or others in charge. Then if they show it to the douche bag, he'll know he's on video. Maybe that'll make him self-conscious about things.
It's easy to lie about how often you have the mask on or off, but when there's video of it, it makes it harder to BS.
Also, if you let it be known you have proof that rules are being broken, that may pressure the owner and those in charge to take a more forceful hand in dealing with things. Because if something bad happens, and the owner and people in charge didn't do enough, they may get in serious trouble.
As for hurt feeling and awkward situations, I say who gives a f***. Better that than having someone die because of this. If he doesn't want to wear a mask, that's his right. But he has no right to expose others to the consequences of his stupidity.
Think about it this way. It'd be a shame if you're daughter and his can no longer be friends because of this, but what if his actions caused your daughter to get it or you to get it or it spreads to your family and friends through you? And gosh forbid. What if the worst possible outcomes results? A few hurt feelings and a lost friend don't seem to measure up, does it?
I can't remember where I read this, so take it with a grain of salt, but I read that all it takes is 1 in 6 people to not give a f*** to perpetuate the spread.
So f*** this guy and his wilful ignorance.