The bulk of the criticism from rational people that I hear is due to the "but they do need to adapt" argument. Flagrantly violating the law just because you want the law to change is not the proper way to do this. If Airbnb wanted to form this industry and generate revenue for cities and offer protections for renters, rentees, and residents in the buildings the units reside in, they would attempt to change the law through legislature. The fact that they simply keep raking in profits from users obviously violating the law paints them in a very negative light to any rational resident of a city where Airbnb is illegal.
They are in a sweet spot right now, where they get to compete with commercial business, but with nearly no regulations. Essentially, they are commerce where it comes to profits, but "sharing someone's home" where it comes to regulations.
It's kind of like running a restaurant out of your dining room, but claiming that the government has no right to inspect your kitchen, because you're "sharing" meals. If I invite friends over for dinner, I should be careful about food prep, but the government clearly doesn't have the right to suddenly show up and inspect my counters and refrigerator.
But if I start charging and serving a large number of meals this way? Totally different game.
Its not completely unreasonable to break the law to protest it when you find it unreasonable. On the other hand, you need to understand that, in doing so, you may be fined or do jail time for your actions.
That's called civil disobedience. I consider it more legit if it is done by individuals for social change rather than for profit companies to make money.
As an individual, yes. Airbnb is more like facilitating individuals breaking the law (or their contract ie lease), so most of the culpability falls on the individual, not on Airbnb.