Some people are anti-Semites (definition: they hate Jews).
Not necessarily do anti-Semites hate ALL Jews (they love saying some of my best friends are Jewish).
To be an anti-Semite, there is no requirement to be a goy. A Jew can also qualify as an anti-Semite. All that is required is to hate SOME Jews.
The way to show others that you hate Jews (are an anti-Semite) is by badmouthing Jews. (Again, no need to bad mouth all Jews, it is enough to bad mouth SOME Jews).
Comments posted here that badmouth ANY Jews is simply anti-Semitic. Sad, if the posters are Jewish, but if so,their yichus is suspect, and needs bdika.