The algorithm does not radicalise people. While it is true that people discover new things that they might never have found otherwise, those are almost always things they would have liked anyway.
To give an example from my own life: Youtube recently showed me
a popular machine repair video. I watched it and liked it. Algorithm responds by recommending more machine repair. But it didn't stop there – after that it recommended a bunch of
other videos with a similar audience, going from machine repair to
woodturning, until it found out that I
really like the woodturning ones, and starts recommending a whole bunch of them. I gained such an appreciation for the craft that I even went and bought myself a hand-turned bowl from Etsy.
Here's the thing though - I always thought woodturning was kinda cool. It just never crossed my mind that there'd be an entire genre of woodturning videos out there. So despite obvious appearances, this is
not evidence of Youtube
making me like woodturning, but rather Youtube tapping into my
existing interest in the craft, which hitherto lacked an outlet. Although if you're a complete
dumbass journalist, I could see how you might think the former.
The same argument can and does apply to trans influencers on the internet - do they
make people trans? Or do they simply tap into an
existing desire to become the other gender? People like Ash (and ContraPoints has said it too) don't think they have
any influence about whether or not a person is trans. And I actually kinda agree with them in a limited sense - the internet is usually not the main cause of people thinking they're trans. The social contagion exists, but it's more likely to be spread by friends and family members (or teachers if a person is young enough).
The type of social contagion that spreads via the internet tends to come from people you know personally (e.g. on Discord, or mutuals on Twitter) rather than influencers with a large audience. If a friend says 'I think I might be trans' and you show them an Ash Hardell video, it's more your fault than hers if the friend comes away thinking they're trans.
However, if your friend types 'I think I might be trans' into a search engine, I don't think it's the search engine's responsibility to steer them towards or away from a certain type of content. Recommendation algorithms should be the same in this regard. If a person keeps getting shown a certain type of video, they should be smart enough to know the algo usually shows people more of what they've already expressed interest in. And if they're too young to understand that, then they shouldn't be on social media.
Influencers have
some responsibility for their ideas, but ultimately it's down to individuals to decide whether or not those people get an audience. But the algorithm (pre Youtube's attempts to nerf it) is not responsible. It's just a piece of tech that shows people more of what they want.