> If the RS doesn't expel people for their politics, then it doesn't make sense to expel Musk for, essentially, concerns about his politics.

But the article does not talk about Musk's political opinion per se. The concerns would have been totally the same if Musk was acting the same way but involving himself with a different political ideology.

The concerns seem to be: 1) Musk is aggressive towards his fellow scientists, 2) Musk is supporting and spreading anti-science things, 3) Musk is pushing for anti-science practices in his own scientifically linked activities (such as not following the steps that guarantee good science in clinical trials).

The article mentions that Musk is getting more political. However, the message is not "being political is the reason why he should be excluded", the message is "while it is possible to be political and continue to adhere to the scientific practice, what we see is that Musk gets more and more anti-science because he gets more and more political".

I understand where you're coming from but because of Covid and those years, using the shield of 'science' to disallow criticism is a little underhanded. Covid/Vaccines/Lockdowns are on the table of politics for the foreseeable future.

Did you even read it?

  The letter specifically mentioned the way Musk had used his platform on X to make unjustified and divisive statements that served to inflame right-wing thuggery and racist violence in the UK.
  I gather that at this point the Royal Society Council opted to consult a top lawyer to determine whether Musk's behaviour breached their Code of Conduct.