That's like claiming that most people talking about the subjugation of women and girls in Iran are only doing so as an opportunity to bash Islam. Even if this unevidenced claim was true, women are still being treated appallingly, regardless of anyone's motivations for raising the issue.
For your information, I have talked to women adversely affected by male athletes competing in their leagues. The issue is not particularly complex to understand, most people can easily see the inherent unfairness in this.
> but it sure is tedious to hear folks with no interest in sports who suddenly have an opinion on who can compete
Clearly they do have an interest in sports - on the topic of fairness for female athletes at the very least - if they have formed an opinion on this topic.
So you never looked into these communities, yet you're painting them as "anti-trans" despite having never read a single post or comment? That seems to be a rather fact-free analysis.
If you had even just casually browsed them you'd see these were subreddits created by women, for women, and focused on the rights of women to have female-only spaces. And that is why they were banned.
It usually is. Reddit in particular banned a whole swathe of women-focused communities, and users who commented in them, where women were advocating for their rights regarding female-only spaces.
Outside of social media, there is a significant amount of institutional censorship on this topic, favoring male privilege over women's rights.