I have a hard time conjuring sympathy for people who over leveraged themselves financially in an attempt to corner the market.
Unless your business is one where if you fail the whole of society is severely harmed I'm not interested in bailing you out. Capitalism is about taking risks, sometimes you win and sometimes you lose.
But I also don't have an issue with AirBnB asking for donations, people are free to give to others as they see fit. And it might very well make sense to help out a former host you appreciated staying with and wish to again in the future.
Now, if they started adding a surcharge, well, that would be a problem.