And if you were too much of a lazy douche to fill out a couple extra fields, they're supposed to believe you'd go through the actual effort of becoming a donor because...?
I'm sorry, you're under the impression people who think of helping this man are under obligation to do so.
Anything that makes more successful donations less likely is bad. Asking for invasive personal information without justifying it in such a way that people are comfortable giving it is BAD.
The fact the guy you're responding to points out something on a site with enough gravitas that is an impediment to the process isn't douchey, it's being helpful. He may be literally saving lives by getting people to improve the process to get more matches.
I'm sure getting everyone to walk to a hospital and pay their own way to take a sample would be a much more convenient way for the marrow matching service to work, however, I be far fewer people would do it.
Same principle with forms that ask for scary data. Not doing so, and doing things in user friendly ways may get one or two more people the marrow they desperately need.
None of which helps if you would have been a match but instead dropped out of their signup process.