I’ve moved a lot of threads from GD and Elections to the Pit. The most common reason is that they are in fact rants that are placed in the wrong forum. Typically this is done fairly early in the thread. My general approach is that after a thread has gone on past an inconsistent arbitrary length, it can be disruptive to move it at all as the rules per each forum can be different and the difference can be jarring.
That being said, it’s context dependent and ultimately the goal is to foster discussion, not stifle it. In some instances that can take the form of closing a thread to ward off potential bad behavior, it could take the form of moving to a more appropriate forum including the Pit, it could take the form of providing constraints to the discussion, etc.