Car modding has a) very high up-front costs, relative to developing political ideas and b) arguably very little chance of doing large-scale damage to a society.
If car modding videos led you down a rabbit hole towards "watch how fast I can go if I cut the brake lines with these $3 wire cutters! Those braking requirements are just a conspiracy between big auto and the shadow government to keep you from reaching car enlightenment, so make sure to drive through the front window of your nearest car dealership"... and then people started doing that, we would have a different attitude about them.
Are they going to take the same stance to videos about gaming, because gaming addiction is a real problem and a progressive diet of “Lets Plays” normalizes unhealthy amounts of video games, by showing people whose entire life is video games?
I can't believe I have to say this, but it's different because political beliefs, whether they inspire one to shoot a bunch of people or just to vote for the "burn it all down" party can have a damaging influence over society as a whole. I.e. it's not just about the personal responsibility to oneself as much as the risk of being inspired to terrorism.
The banning of dissent under the pretense of radicalism has harmed more people than terrorism — Stalin’s purges, Mao’s purges, heck, even Hitler was just clearing out the seditious members of society who were undermining a strong Germany.
Your arguments, however you mean them, are also those used by tyrannical oppressors to justify the powers they use to commit great evil.
In an (unintentional?) irony, all of those people you cited rose to power and did great damage to their societies by exploiting radicalism in politics.
Gaming addiction is a systemic problem that’s impacting the social stability of several Asian nations, and possibly Western ones — your argument isn’t principled, merely special pleading.
It was just an example, but who are you to say it’s not already a huge problem? It surely is to somebody. Maybe they work at YouTube. Modified vehicles spew enormous amounts of pollution into the environment which as we all know is a huge crisis. Driving highly modified vehicles on public roads is also a huge public safety hazard. Nobody needs 1000 horsepower on public roads. See how this can get out of hand? It all depends on who is deciding what is problematic.
If car modding videos led you down a rabbit hole towards "watch how fast I can go if I cut the brake lines with these $3 wire cutters! Those braking requirements are just a conspiracy between big auto and the shadow government to keep you from reaching car enlightenment, so make sure to drive through the front window of your nearest car dealership"... and then people started doing that, we would have a different attitude about them.