I don't have a moral objection to firms insisting that executives participate in charitable events, just trying to understand the situation.
He might now be sufficiently senior that his conduct, including charitable activities, reflects on the firm. If so, and the firm takes these things seriously, then he will have to get with the program if he wants move up. Of course, if no one takes it seriously, and it is just a chance to go to a few parties, then perhaps no one cares. If they take the charities seriously, but not so much being seen there, then he may be able to make even larger donations- and get credit for that- without having to show up in a monkey suit. In any case, renting a tux sounds like a bad move. He can buy one for less than the rental price. I suspect no one rents particularly nice tuxedos, so he is probably going to appear in something fairly low brow either way. If the firm cares about that, then he may have to suck it up and come to event dressed as they expect. As others have pointed out, suits are not cheap either, and he wears them to work because he has to. This does not seem any different.
And he should be grateful he is in a position to be able to give to charity, rather than having to rely on it.
