I’ve argued in some of the posts below that it’s a lot — including statements that by themselves don’t satisfy the criteria for liability, but that reasonable employers have to suppress in order to prevent liability. For a pretty detailed explanation (and lots of citations) as to workplace harassment law, see here. I wrote it in 1997 (elaborating on what I had written in 1992), and updated it on occasion over the following years; but it should still be accurate, though I could beef up the examples still further with later cases.
For more on hostile public accommodations environment harassment law, see here. For more on hostile educational environment harassment law, see here, though that’s much less comprehensive than my coverage of hostile work environment law or hostile public accommodations environment law.