The term "Democrat Party" (and, more generally, "Democrat" as an adjective) is both a shibboleth signaling opposing tribal membership, and an epithet signaling

The term "Democrat Party" (and, more generally, "Democrat" as an adjective) is both a shibboleth signaling opposing tribal membership, and an epithet signaling contempt for the Democratic Party — the actual name of the organization. It's adult name-calling. The usage is widely understood to be an intentional discourtesy.