If he had said your opinion is shit because you're an asshole, he would have been arguing towards your person, in other words, presenting an argumentum ad hominem. Instead he told you to try harder, asshole. That is a command and a command cannot be true or false since it is imperative rather than affirmative. There is no fallacy in what he said. You didn't even offer an opinion on Dreamcatcher for him to dispute, you just said you personally couldn't find them interesting.