Speech is a form of power. Decisions about which speech is allowed affect the distributions of power and it's easy to see how the decision to ban politics is itself political.
In this sense it's not possible to ban politics from HN, only to change the distribution of politics.
We should examine the ways that a ban like this might change the distributions of politics and power among the HN community. I suspect we'd find it reduces the power among marginalized communities. Even if you're not from one of those communities you can really benefit by reading their writings. In that case to cut off those voices is a shame. It's a loss.
Who's deciding what counts as political and not? Moderators. We should examine that. "Banning politics" essentially becomes "Moderators politics."