if a 15% hotel tax is what steers you away from one of the world's preeminent tourist destinations, I'm not sure that you were going to add much to the local economy.
(To be a little less snarky, the microeconomics of the situation indicate it's probably not that damaging. Your hotel stay is probably less than half of your costs of visiting, so a 15% markup on that component alone doesn't raise the overall price of a trip very much.)
It's not like there's a shortage of people who want to go to new york and can spare the extra 15% though, is it? The city was packed to the rafters long before Air BnB came along to 'disrupt' everything.
(To be a little less snarky, the microeconomics of the situation indicate it's probably not that damaging. Your hotel stay is probably less than half of your costs of visiting, so a 15% markup on that component alone doesn't raise the overall price of a trip very much.)