Disparaging a type based on one person of that type is another kind of bias. The reasoning goes like this "I hate my (mom, dad, sister, grandmother) who's X, therefore I hate all Xs."
Someone will post (often in an Introduction thread) "And I can't stand ISFJs" [or even SJs]. Inevitably it comes out the person hates his mother whom he's determined is an ISFJ. We see this over and over again.