Let's be clear, the 'activism' in question (at basecamp) is anti-racism. And if anti-racism is a competing cult, then you might want to switch sides.

Being unable to countenance good faith disagreement is not a persuasive argument against your ideology being a cult.

As an alternative approach, you can cut the gordian knot of being against anti-racism without being in favor of racism by simply noting that the thing is not what it calls itself.