Tolerance of people and tolerance of actions are two separate things.
Tolerance of thoughts belong in the former, intolerance of intolerance into latter.
Tolerance of people (thoughts, ideas, personalities, everything that doesn't affect anyone else) should be pretty clear. Voltaire said it perhaps the best: "I disapprove of what you say, but I will defend to the death your right to say it."
Tolerance of actions (things that affect other people) is a different matter altogether, and is not quite so simple matter to place into a group of things that should or should not be tolerated... However, I'd say that in most cases* it is the opinion of the affected that defines the category. If you are hurt or insulted by someone's actions, you don't need to tolerate it. In the Internet the obvious correct course of action regarding idiots is to distance yourself from the argument abuse rather than get sucked into a mutual virtual excrement flinging contest to the trolls' amusement.
Of course, no one's there to ask the murder victims' opinions, yet we place that sort of behaviour strictly to "not tolerated", except if it's done in great numbers and to the sounds of trumpets, but that's a different matter. Of course, tolerance of euthanasia touches this one pretty close...
*Cases where the opinion of the affected is not considered important [EDIT: or valid] are pretty interesting case in themselves by the way. As a homework - in which cases it would be acceptable to use general opinion as the authority of placement into "tolerated" or "not tolerated" category?