The BBC asks, was the Manchester Arena bomber radicalised ..
It seems to me that 2 things are being confused or conflated here: incitement to carry out a terrorist bombing in the UK for its alleged complicity, or to join ISIL (IS), both of which are unequivocally condemnable; and incitement to going to Syria to fight against Bashar al-Assad, which is illegal under UK law, but, morally, far more ambivalent.
Perhaps I should clarify: plenty of people have been convicted for going to Syria; no-one, as far as I am aware, has been convicted for inciting that. To do so, in my view, would be a dangerous extension of restriction of freedom of speech.
Further comments here on the group formerly known as Nusra Front or Jabhat al-Nusra.