Maybe I'm confused. How is it no different when they're mandating it to participate in an event? They're not asking for a donation to USAC on the registration page. Donations tend to imply a voluntary gift, usually monetary, to an organization they support or believe in. There's a lot of people who do not believe in, or support, the USAC/UCI and also don't care about points.
BTw, I'm not trying to dissuade anyone from signing up for h2h. There's no shortage of events, sanctioned or not, for people to choose from.