If your father is using those words as an insult, he is probably a maga or close. Being leftist is only an insult if you are an empathy-lacking rightwinger that sees people defending human rights as an enemy; be it because they've been brainwashed or because they are evil.
In any case, be proud, if a maga sees you as a leftist, it means you are a threat to the fascism they want to bring to the world. And my advice is to not seek acceptance from them too hard, chances are they are white supremacists not caring for anything remotely "different". Acceptance comes from people capable of empathising, and magas are... not ready for that.