Airbnb now claims to be the size of, say, Albuquerque: one of the cities where I grew up, with somewhere around half a million people. In Albuquerque, there are 200 reports of vandalism, 100 stolen cars, 100 burglaries, 50 aggravated assaults, 10 kidnappings, 10 forcible rapes, two acts of arson, and one homicide, according to http://www.cabq.gov/onlinesvcs/crimestats/.
Every week.
EVERY WEEK. A murder every week. Fifty aggravated assaults every week. 200 reports of vandalism every week.
From this we can draw three conclusions:
1. You're probably right that there are other incidents. Probably some vandalism and assaults, maybe even some homicides.
2. Airbnb is a lot smaller than it appears to be. Maybe it's more like a 10 000 person town than like a million-person city. Maybe that's because their average user only use their service for a week every year as either a guest or a host.
3. Even so, Airbnb is a hell of a lot safer than Albuquerque, or actually any city in the US. An Airbnb user is a more likely to get kidnapped or murdered just at random than by someone they met through Airbnb. And that's probably still true even if you just consider the time they're actively using Airbnb.