Can art be damaging?
If we accept my definition of art as Objects made for the purposes of contemplation then art functions as a locus of thought, ideas, discussion and debate.
In American culture, the notion of Freedom of Speech trusts that in the debate over ideas, "good" ideas will eventually triumph over "bad" ones. If we have this faith, then we must allow art must provide a net benefit as a stimulator of ideas. We tolerate ideas we find reprehensible in the believe that better ideas will predominate.
But a corollary to my definition is that while an object may have a value as art, it may be a repository of other values; economic, utilitarian, decorative... And it may, and often does, function as advertising and propaganda, which we believe to be effective in persuasion for good or ill, or we wouldn't see so much of it.