I may be off here, but I believe that they are referring to the political aspect of the word “radicalize”. In a standard democracy, it’s not really appropriate for the government to attempt to halt the spread of competing philosophies that may result in electoral changes. (This doesn’t apply to so-called “defensive democracies” as well as “guided democracies” which IMO aren’t really democracies.)

The problem in these discussions is that radicalize is an overloaded term. It could mean convincing someone of your non-mainstream political view, or it could mean inspiring someone to commit an act of terror. The former seems perfectly fine to me and well within freedom of speech and association.