I suppose that depends partially on how closely things that unnerve the parents are correlated with things that will traumatize the children, or influence them

I suppose that depends partially on how closely things that unnerve the parents are correlated with things that will traumatize the children, or influence them to emulate undesirable behaviors. And I don't think a parent's discomfort is sufficient, either. There were things that I watched as a child, with my parents' knowledge, that I still consider to have caused me trauma.