The term is “hostile work environment”. HR doesn’t just respond because of strict liability. Just one occurance of something like this can lead to an otherwise solid worker to spiral from discomfort of the situation, both feeling like a prisoner at their job and producing far less value for their employers.
The latter is why HR cares, but the former is why it’s OKay to go straight to HR. If HR is well-trained, things like this shouldn’t escalate just because you went to HR. They should be able to diffuse it productively.