Disclaimer- in this reply I may use some offensive statements as examples, none of which I agree with. To summarize my actual views- I consider myself liberal-libertarian-- I believe the married gay couple should have guns to protect their pot farm and legally adopted children from harm, knowing that single payer healthcare will prevent them from going bankrupt if one gets hurt. I don't care which bathroom you use as long as you wash your hands. And I think government should be out of the marriage game, there should be a one size fits all civil union for any couple/throuple/quadruple who want to legally entangle themselves (and it should not say 'marriage' anywhere on it). If you want to get married go to a church, if you want to be legally entangled with your partner go to the government.

In that case, what is the line between “simply” hate speech and actual radicalization to terroristic acts and/or conspiracy to terroristic acts and/or incitement to terroristic acts?

There's two lines. The line I'm more concerned with (and you should be too), is where's the line between 'simply' a controversial opinion, and 'actual' hate speech. If platforms are required by law to ban 'hate speech' then where does that line get drawn and by whom? And how do you differentiate between a controversial but honest opinion, and a prejudiced and hateful statement, when the two share the same position?

For example, is 'gay people freak me out' an opinion or hate speech? What about 'I don't think gay people should be allowed to adopt children because it could harm the children'? What about 'I don't think gay people should be allowed to marry because marriage is supposed to be a man and a woman'? Are those opinions or hate speech? Is there a difference between 'I don't think gay people should be allowed to adopt children because it might harm the children' and 'I don't think gay people should be allowed to adopt children because fuck the gays'?

Depending on how you define 'hate speech', it might require platforms to themselves remove anything even vaguely anti-gay.

I have no problem with any private platform choosing to adopt whatever rules they want. I have a BIG problem with government-mandated censorship of controversial opinions (and I think you should also).

As for the two lines, let's do a spectrum--- again, this is presented as an example, I do not agree with any of the following statements.

1. I don't like gay people.
2. I don't think gay people should be allowed to adopt children because it would harm the children.
3. I don't think gay people should be allowed to marry because it's bad for society.
4. I don't think gay people should be allowed to marry or adopt because I hate gay people.
5. I don't think gay people should have the same rights as straight people.
6. I don't think gay people should have traditional civil rights.
7. I don't think we should tolerate gay people in our society.
8. I think we should send a message to gay people that they're not welcome.
9. I think we should round up the gay people and kick them out of town.
10. I think gay people are a cancer on society that should be excised.
11. I can understand why someone would want to get rid of gay people.
12. I think it's reasonable to want to get rid of gay people.
13. I want to hurt gay people and you should too.
14. I want to help get rid of gay people by any means necessary.
15. It's time to take up arms against the gay people infiltrating our society.
16. I'm going to get my gun and go shoot some gay people.
17. You all should get your guns and go shoot some gay people.
18. We're meeting at 8pm at (place) to pass out guns, then we're going to (gay nightclub) to shoot gay people. Come join us!

Where do YOU draw the line in there?
For me I'd say the line between opinion and hatred is between 3 and 4, and the line between hate speech and criminal incitement is between 12 and 13.

The problem though is if 'ban hate speech' is codified into law, if platforms are REQUIRED to police it, then ALL of this becomes essentially illegal to say, essentially starting with #1. And while it's sad that anyone would say any of this, that basically makes it illegal to express ANY dislike of gay people because of the murkiness of the line between unfortunate opinion and hate speech.