I don’t think anyone is saying he should have done a bad job for his client. If you are hired to defend a murderer, then do it, so be it. But just let it be, don’t try to play both sides.
I can’t speak to his mind, but I interpret what he is saying that he would work for anybody who hires him.
I will agree that, even if what he said is true, he probably shouldn’t have said that. He’s just basically saying that whatever their loss, it was partly their fault for not hiring him. Which is a tasteless thing to say.