If social norms change and you want your group to have continued legitimacy, you may need to change with them. Not having a code of conduct doesn't make things any different.
The you'd describe being apolitical as not being "legitimate" is chilling.
In some sense, what I'm saying is that it's not possible to be apolitical. Politics is just lens through which we analyze human interaction. You can't have social groups without politics.
If you mean specifically "politics" in the US democratic/republican party sense, that's in theory a more attainable goal, but keep in mind that under that definition you excuse what is objectively bad behavior (IBM supporting the Nazis, as an example). Not to mention that the political parties in some sense have a vested interest in making things that shouldn't be political issues "political".
And you also get into the question of what is political? Are facts political? Is saying "black people are killed by police at a higher rate than white people" political? You're ultimately just advocating for a different form of censorship, which is fraught with all the same problems as any other form, but additionally with the duty to appear unbiased in how you define what is or isn't political.
That's an inherently conservative position to take. Which you should recognize if you want to take it.
Until a topic (think BLM kind) came along that people thought should be an exception; The usual arguments: this wasn't politics, this was basic human rights / existence; It was offensive not to allow, is was oppression to not discuss.
Basically, enough people cared more about <topic> than their continued membership, or even the continued existence/stability of the group, that may become fractured by <topic>, that they where willing to leave and make a big stink about doing so, enough to potentially give the group a bad reputation, and leveraged this threat against the policy.