A self-proclaimed gay, Jewish white supremacist was in court last night ... facing charges that he has terrorized Anderson Cooper, threatening to "f**k you up."
40-year-old Alex Hausner has allegedly stalked Cooper for 5 years ... but things escalated last month when he showed up at the CNN star's home, trying to kick down the front door of the converted firehouse and screaming, "I swear to f**king God, don't insult me. I'm going to f**k you up."
According to the New York Post, Hausner has made numerous threatening phone calls and attempted to get face-to-face encounters with A.C. for years. The Post says Hausner also targeted Anderson's boyfriend, calling him a "thug" and a "mongrel."
Hausner -- a psychiatric patient -- faces felony menacing charges and misdemeanor harassment charges. He's being held on $75K bail.