I have repeatedly presented evidence to support my position, you haven't presented any. You've just made blanket statements and ignored the umbrella groups aligned with them.
You attempt to present the FSI as simply a Union, just like any other. But they aren't. Most of their funding comes from donors not members, eg Mark Hillery gave them £400,000. They don't declare most of their donations, but given people like Charlie Vaughan are involved, there is clearly some serious financial backing.
The FSU champion the incel's hero, Jordan Peterson, the guy who argues (against all evidence) that gender & class hierarchies are the result of the natural order. Supporting a false narrative is not the same as supporting free speech.
Some things are actually bad, the racism, misogyny, class eugenics they support is worse than the equality, queer theory or critical theory they oppose.
Name a Union that takes action on behalf of a non member? That would be every Trade Union, they work for better pay and conditions in the workplace for all employees not just members. The FSU just last week were trumpeting taking up their "biggest case ever", the Newcastle fan investigated over anti-trans social media posts. Yet they were conspicuously quiet about the Liverpool fans having Free Palestine flags & clothing confiscated.
Now, let's look at the Thiel https://www.varsity.co.uk/news/22640
Now, how about you come up with some evidence that the FSU aren't ideologically driven?