At a certain point, people get in this so deep that it becomes a religion, and unfortunately logic doesn't help in these cases.

That only happens if they are engaged in healthy discussion. A flame war separated into two columns isn't that.

Have you ever tried to argue with someone who is into conspiracy theories?

One of my former best friends went down the deep end. It started with 9/11 conspiracies and just spiralled down from there.

I engaged with him, because I care deeply about him, but it just got worse and worse. Initially it was 9/11 and questions about wealth and power distribution and there are some valid questions that can be asked (although all the 9/11 stuff is bonkers). It soon became crazier and crazier, it was about "energy from the vacuum" (essentially a code-word for perpetual motion), how Gates is trying to sterilize the population through vaccination.

The irony was that he was seeing himself as a freedom fighter who is speaking the truth to prevent the next fascist regime, completely ignoring that many of the people he followed or supported were literal Nazis.

Engaging with him was not possible. He would bombard me with links that somehow were supposed to proof his point. If I brought up counterarguments, he would say that he has strong evidence that one can not believe mainstream media, science, logic ... And that I'm just a sheep blindly following "propaganda" and he knows better.

There was absolutely no way of getting through to him or engaging in any kind of discussion. This was just his monologues and flooding me links (many I suspect he did not even read/watch).

In the end I had to cut contact, because it was affecting me mentally, the interactions would just leave me exhausted angry and incredibly sad.

I don't have a solution, we need to somehow find a way of how people can be drawn into these crazy web of conspiracies and I don't think that creating forums were these crazy things are debated like they are valid opinions is an answer.

Flat earthers are not going to change their minds based on logic. They are bombarded with evidence and logic any time they mention their beliefs. Contrary information often entrenches their wrong beliefs even further.