That time I was douped

I don't understand where people get the motivation to take advantage of others.
Well, I'm taking about one man in particular Daniel McMahon of Vancouver, BC.
On Pinkbike, his username is PartHoe.

He sold me a used Cove Shocker frame, I was ecstatic. My first Cove Shocker, f*ck yeah! Except the Medium frame size he advertised was a small. When I asked "what condition is the frame in?", he replied "there's a little bit of chainslap but nothing major."; that was not true. There is a major dent to the underside of the down-tube (likely from careless shuttling), and another at the top-tube/down-tube junction on the drive side (looks like a strike from a double clamp fork stanchion). After cleaning the frame thoroughly, it was filthy at purchase, I even noticed a small crack ahead of the forward shock mount, non-drive side. Cove Bike Shop confirmed this, but all he was willing to do was deny it. I'd love to take him to small claims court, but the fact of the matter is it's just not worth my time.
Still has the buy-sell add on his profile, disgust.

I am a mountain biker. Just like you. We have a common bond. I think of us as brothers and sisters of the same chain-gang. Trail friends with a common cause. I don't believe that this individual thinks the same.