I'm not saying a reasonable person looking in from the outside couldn't think they were frivolous. I'm just saying the PSF leadership themselves didn't think they were.
I personally, looking in from the outside, wouldn't necessarily describe the reasons as "frivolous", but I think "unjustified" certainly fits the bill.
It's not even much of an inference. The discussion went sideways because Steering Council members in the thread kept responding to Tim's questions about why the proposed bylaws change was being made (and pushed through very quickly with no real discussion) by saying "there are reasons, but they're secret and we can't talk about them, trust us", and getting very hot and bothered when that answer was not accepted (and not just by Tim, there were multiple people in the thread who were not satisfied with it and explained why at some length).
After quite a bit of back and forth, one SC member (I think Thomas Wouters but I'm not sure) admitted that there were specific PSF Fellows (giving no names) who the Board planned to use this new power to remove. And it's at this point that Tim's ban becomes even more of a footgun on the PSF's part, because when Tim saw this, he said that knowing it made him more likely to vote for the proposed bylaw change, since apparently the need for it was not just hypothetical. (Others in the thread took a much more negative view of the revelation than Tim did.) So the whole discussion that Tim prompted ended up with Tim supporting what the PSF were doing in this case--which should have been a cue for the PSF to say, hey, good, I'm glad we've addressed your concern and you're ok with this now. But instead--they banned him.
One could infer that the core of the issue is that Tim started to ask questions about why the board would grant itself additional powers (see bylaws), advocating for transparency and accountability. They were not happy about that and locked the discussion.
Then they started to look around for reasons to tint his reputation and ban him.
Look at this open discussion/question (https://discuss.python.org/t/how-can-we-better-support-neuro...) from Tim to know whether neurodivergent people were accepted by the Python community, and how they framed it as:
"Dismissing unacceptable behavior of others as a “neurodivergent” trait, which is problematic because it creates a stereotype that neurodivergent people are hard to interact with and need special treatment."
Which was one of the reasons of the ban.
They even considered the use of the wink emoji to be harmful, apparently.
https://chrismcdonough.substack.com/p/the-shameful-defenestr...