This is what I think happened . . .

Scott was getting jealous that B and Dawn began to connect. When he learned she might have feelings for him, and possibly he did too he didn't want B to stand in there way. He set him up too fail. B was gone and maybe off camera he saw Dawn connecting with him. Because he probably wasn't ever in a relationship or anything he got scared. So he then set Dawn up too fail. Because instead of dealing with his problems he just pushes them away.