Dirty sheets and a stoned airbnb host

I have used Airbnb a number of times without incidence. The best was in Barcelona for an incredibly low rate at a modest, but clean and convenient location. Early this summer I booked a night in Montreal for my daughter and me. We had a full day attending the Women’s World Cup and really just needed a place close to the stadium to sleep. Our host greeted us casually, directed us to a room near the entrance of her apartment. She showed us where the bath was and went off towards her own room. The bathroom had dirty wet towels and other people’s wash cloths in the shower- it was clear that the bathroom had not been cleaned in advance- The room was like a dorm room, with random belongings of other guests? The sheets had clearly not been changed and had hair on them. My daughter and I were sharing a full sized bed- She had fallen asleep and soon after I laid down I felt something crawling on me- I lifted the sheets and there were a half dozen gnats in them. I went to the door of our host and knocked- she opened the door- I asked if the sheets had been changed and she was not clear- not just because she hadn’t been involved in the process but she was quite stoned. She seemed confused, baffled that there was an issue and said her roommate had changed the sheets. I asked if there was another set and she said that there was not. I was tired and freaked out by the bugs and said we would not stay. My daughter and I drove through the night to get home. When I called Airbnb the next morning to request a refund I was told (after nearly an hour on the phone just trying to get a person) that it was up to my host to decide whether or not she was willing to give me a refund. I repeatedly asked if Airbnb provides any protection for people who need a place to stay and was told that they are just acting as the advertisement/agent for the host. If this is the case and there is no protection for the renter/traveler/guest I am unlikely to use Airbnb again. I do not trust that I will not be scammed or taken advantage of and after the apathetic response of the Airbnb staff I am not interested in having to negotiate a refund for a stay in a dirty apartment. I travel a lot and want peace of mind about my destination. I want the key that I am given to fit in the door that was advertised and I do not have faith any longer that this will be a given with Airbnb. I think they grew too big too fast to manage the challenges that they now face.