It's pretty simple. If the user can't pre-screen and validate the guest's identity before renting, the onus is on Airbnb to ensure that they will not destroy your home.
Besides, that's the only way this company can work at scale. Without trust in the system, who will use it?
Try to divorce yourself from the topic and read your reply again, realizing that you've set up an impossible standard and blanket-judged a complicated balance of liabilities as "pretty simple."
The problem for any organization dealing with a large volume of possible cases is that you need to figure out where to draw the line. Preferably you want it in some place that is transparent and easily communicated to people. Otherwise you'll have an endless stream of cases close to the line with arbitrary outcomes that you can't explain.
Clearly, "So and so drilled through my walls to steal my stuff" should be on the far end of the line. Clearly, "So and so stole my pencil" should be on the near side of the line. But where do you draw it in the middle? With the claim of a broken TV? With a hole in the wall?
Even if AirBnb had a way to check this guy out, it's quite possible he doesn't habitually destroy homes and steal people's identities.
Dunno. That's going to be Airbnb's problem to solve if they want to enjoy ongoing business. That's their job if they want to be the "Ebay of spaces."
If your argument is based on the assumption that hosts can not screen guests then your argument is wrong.