Secondly: Is the statement true, that errorists are intellectual idealist per se, or does that just help? Subquestion, where the other european terrorists (excluding ETA, IRA, as they are somewhat different), but I seem to recall Belgian and French terrorist cells, were they equally educated?

Core IRA terrorists tended to pretty well educated as well: probably one of the reasons for the relative ineffectiveness of loyalist terrorists was the lack of an intellectual core. The loyalists could riot, they could shoot people, but they could never put together a proper terrorist campaign that I remember.