I dealt with a lot of SJWs in my high school experience. Towards the end of HS, I enrolled with my tribe (1/2 Creek), so I could just deflect allegations of racism with 0 effort by pulling out my literal race card.
Prior to that, I just used their kryptonite; ask them to explain their views. Ask them to cite sources. Ask them why.
Usually you get the typical "are you kidding me?" or something similar, but that just means that you've beaten them. If they can't engage in any sort of intelligent conversation about politics, they shouldn't be shouting their political views to the masses.