It doesn't solve it but it definitely helps in some cases: http://comp.social.gatech.edu/papers/cscw18-chand-hate.pdf
Because it doesn't have a 100% success rate doesn't mean it shouldn't be considered, otherwise we could use the same logic to dismiss basically any rule, law or regulation ever made.
Echo chambers are never a good thing, echo chambers built around hateful extremist ideologies are a lot worse. By forcing these people to get out of them some good can be achieved. Of course some of them will manage to regroup elsewhere but statistically a significant proportion will return to a more healthy lifestyle.