I think - correctly or incorrectly - a lot of people perceive the typical Burning Man attendee nowadays as being a rich and/or famous person who is somewhere between indifferent to + amused by the suffering of other people less fortunate than they. And - again, not saying this is correct - they perceive this as being more of an annoying/inconvenient/uncomfortable thing (lots of wallowing in filth, but only 1 death AFAIK) than a bona fide natural disaster; totally different order of magnitude from what just happened in Florida, for example, or Hawaii.
So it's less serious than a hurricane or flood or whatever in a populated area, and affects much more deserving people; if, heaven forbid, a bomb went off and hundreds of Burning Man attendees died it would be a very different story, and certainly in that case I don't think any decent person would laugh about it, but a bunch of rich assholes stuck in the mud playing "Survivor" for a week is much more farce than tragedy.