I don't handle a lot of employee law at my office, but I've been one for more than 30 years, and I'm pretty sure this guy is creating a hostile and unsafe work environment which is a violation of federal law. Your boss is laying his own job on the line by not acting on your complaints. The rule used in assessing responsibility is that "management knew, or should have known" a situation existed. You've told him, so management knows. Follow the chain of command for grievances. If this is a job you want to keep, then document, document, document. Dates, times, what happened and who else was present when it happened. Good luck.