Ya, it almost seems like once the criticism of the list took on a somewhat political component (people saying it was racist), that the critics were silenced with the no politics rule.

This is basically what happened according to available info [1]. DHH, one of the co-founders, admitted the list was a mistake but aggressively pushed back on the political assertion by some employees that the list and the people involved were contributing to genocidal attitudes. As DHH pushed back, he went so far as to dig up old employee messages and repost them publicly to argue that the employees making accusations about genocidal attitudes were themselves hypocrites. Less than two weeks later, Jason Fried announced the new company policies.

[1] https://www.platformer.news/p/-what-really-happened-at-basec...

According to the summary articles posted upthread, that seems to be what happened. The list was reinterpreted in the context of Stop Asian Hate to be racist. Which is not exactly fair given that the list is 10 years old. One should judge by the standards of the time, not the changing standards of today. And reading between the lines, that's essentially what the Basecamp founders said too: (paraphrasing) "this was a joke in bad taste made by people who aren't even at the company anymore. we're sorry that it happened, but it's water under the bridge." Then someone filed a racism complaint with HR against the founders and it escalated from there.