It does make me question whether Airbnb actually physically matches profile pictures with id (driver's licence, passport). I have been asking Airbnb to give us full names of ALL guests, not just the one booking. I try to check Facebook to see what potential guests have posted, especially if I have concerns.
It put you in an awkward position when he showed up. I would hope you have phoned Airbnb and discussed this with them. If you are like me and live alone we have to be especially careful about who stays with us. In 3 years I have never had a major issue but I have turned down potential guests if my instincts tell me.