You really have to have your head in the sand to deny that white supremacist groups exist and are a serious problem. "Antifa", which is shorthand for anti-fascist, just refers to people who believe in combatting the spread and influence of those groups through direct action.
There's so much ignorance regarding "Antifa". It is literally shorthand for "Anti-fascist". It's an ideology, and it has nothing to do with a "political group". There is no central organization or structure, as there are with several actual white-supremacy / nazi groups such as the proud boys and kkk.