IMO there's very little on the internet that's significantly more toxic than Hollywood movies and pop music. Porn, I guess.
If you do find it: congrats, you must be pretty inventive.
On the extremist content: those people are not well versed. If you reaaaally want to you can let it brainwash you, but at that point a book could do the job as well.
And: internet extremists don't have significant attention spans and can barely act in the world. If they learned how to read, well... they'd soon know better.
Kinda sounds like LSD, or entheogens in general. It's not yet common (AFAIK) but they can be used in conjunction with sources of information, like logging into an administrators account.
Is there evidence for or against the interior of black holes being similar to distinct separate universes? Is that a popular idea at all, in physicists' circles?
How much (and _what_) would I need to read and understand to get a feeling of the nature of black holes?
I'm a total layman when it comes to physics and it would put some distant worries of me to rest.
I'd rather measure a lot of Hawking radiation while throwing bottles in flasks into a black hole. However, I'm currently preoccupied with figuring out why my mouth keeps talking when I'm not thinking of anything.
Telepathy is the only thorough solution I can imagine.
You'd invent and disseminate a viral "spell" that teaches people this.
The spell would convey the thought-form of communicating with the explicit intent of speaking about nothing that would be censored or put you and your loved ones in danger. One effect of this is you learn to communicate via more and more subtle innuendo, because whenever you do speak about dangerous topics anyway you're contradicting yourself and that can be felt. It's key however to communicate without any innuendo at all, and to not hold onto communicating any specific forbidden thing. That will take practice though, so making sure there's an obvious legal interpretation is a good safeguard.
The first thing you'd need to learn is to express that what your conversation partner is saying seems dangerous or shifty (feedback loop, I suppose one could just express discomfort) or could use a better explanation.
It's basically steganography but you don't even construct any explicit message. You train your communication to be more and more formless. Untouchable.
I'm not versed in making spells but this is how I'd imagine it:
"I will never speak to you about anything that would be censored or that would otherwise put you and your loved ones in danger. I have all the freedom I want and need, and I only wish for China to flourish. Don't you? If so, do you mind repeating my words?"
Putting that in a song would be a good one. It could be felt as a scary thing to be told, and to take away that fear where you notice it in others you could teach what it actually does (a second spell is necessary for this, otherwise you'd have to be explicit and that would put you and the recipient in danger). I'm afraid I don't have the means to construct that however.