Second, and more importantly, you seem to neglect the fact that some AirBnB hosts are not just violating laws, but their leases and HOA rules. These are legally-binding contracts between private individuals.
AirBnB's most ardent supporters like to focus on zoning and hospitality laws, suggesting that they're antiquated, anti-competitive, etc. Some of these arguments are quite reasonable in my opinion, but what about private contracts? I have yet to see convincing arguments around the issue of hosts who are violating their contracts with their landlords and/or homeowners associations.
Most apartment leases have strict terms around subletting and many HOAs have restrictions around property use that would be in conflict with AirBnB-style short term rentals. Even if AirBnB doesn't have a legal obligation to help enforce these, given the number of listings that are ostensibly governed by leases and/or HOA rules, it seems implausible that AirBnB isn't aware that a good number of its hosts are breaking private contracts, potentially exposing those hosts, their neighbors and even their "guests" to a variety of risks.
Does AirBnB not have a moral obligation to address this? I'd love to see more AirBnB supporters take on this issue. At least it would be more entertaining and perhaps even more enlightening than the recurrent arguments against zoning and hospitality laws.