Guess what: if you ask your local Catholic priest to give sermons for your weird sect, he'll probably refuse too. And if lots of people keep insisting, it's not surprising he gets annoyed.
Ironically, that's exactly what Microsoft has been saying about Linux during those bad old days. Linux was successful because its developers didn't say "If you want to talk to a professional, buy something else."
I'm not saying an OSS developer should bend over and take abuse from users. But I believe there's a line between that and calling users "entitled brats" just because they use vendor-supplied drivers for their $500 cards.
Except, the reason why Microsoft was wrong was that Red Hat existed. If you're running CentOS or Arch Linux or something, you really are fucked as a business. The key distinction here is that SirCmpwn is not a Red Hat dev, so should not be expected to meet the responsibilities of one.
That's weird. Professionalism should be expected in all aspects of life. That's basic human respect.
If someone offers to paint your fence for free, and your fence has some really nasty angles at some point, would you say the volunteer was unprofessional if they said "yeah I'm not going to paint that part"?