That is, at least to me, is both a bit of a strawman and an invalid comparison.

First: The statement "black people are" implies it applies to all of them, or at least the average person, whereas the sentiment that I usually see isn't that all men are dangerous but rather that some are and it's difficult, if not impossible, to know which are beforehand.

Second: Men have not been marginalized, discriminated, and systematically oppressed for centuries. People of color have been, at the very least in the west and the countries they've colonized.

There's an additional point to be made here that I feel is relevant: Ethnicity does not inherently infer a large difference in physical characteristics the same way biological sex does. I don't imagine the strength of an average person varies as much depending on ethnicity as it does depending on biological sex. The average man is much physically stronger than the average woman, in a physical confrontation she'd be at a distinct disadvantage.