The problem is that the title of the thread and literature offered up in the original post denigrate the opposition and marginalize it to a mental disorder.
This does two things:
First, it trivializes actual mental disorders and those people with them, which is insulting and immature.
Second, it puts one side of the discussion on the defensive through slander before any debate has taken place, thus reducing the chances for a real discussion of political, ideological, and philosophical differences.
Both of these reduce the level of intellectual discourse needed for a civil discussion. Taking this thesis serious is disgraceful and disingenuous, and supports the criticisms of the current polarized political climate.
You don't begin a civil debate by deriding the opposing participants as "crazy".