What do you think happens to people in western countries spreading terrorist propaganda? Right they sent them to prison.
Also western intelligence seems to be not opposed to the concept of early deradicalisation, here is an interesting take from Richard Barrett, former director of global counter-terrorism at MI6:

We need to get to potential terrorists before radicalisation, not afterwards Once an individual has fallen for extremist propaganda, it’s hard to change their mind. Better to spot the early signs