So he isn't actually the god of lies and deciet, that's a derogatory title his enemies bestowed upon him. Fen'Harel = Rebel Wolf. Solas sees himself as neither a god nor a great deciever, though he does lie sometimes of course. As another commenter said, the abhorrence seems to be more about him being accused of doing blood magic in a way he sees as terrible. The whole god of lies banter is a purposeful stab at him, as well