Is it possible to restrict a member to a single or a number of threads where their opinions are valid and stop then posting elsewhere if they are causing friction?
No you can't restrict to single or multiple threads in forums.
You can restrict them to there own threads to view in the Forum Management Permission. Another option is enabling Moderate Posts in User & Groups.
Ok to be sure I understand this. You are saying that we can set up so that a disruptive member can only create and contribute to their own threads?