That they agree with one piece of your politics at this particular moment in their company's growth and at this particular point in the evolution of your political beliefs is a massive red herring.
Let me repeat. Substack is trying to generate returns for venture capitalists.
That said, your point is well-taken. I think one of my other comments already captures my thoughts on the point your making; let's move there to discuss: https://news.ycombinator.com/item?id=30093683
Yes, but they're doing this by countering the heavily editorialized and censored mainstream print media with a more free speech-oriented platform. This is exactly how we should exploit markets to produce good social ends.