The problem is that "shallow cynicism", "gratuitous negativity", and "all forms of meanness" are vague distinctions all subject to interpretation.

Guidelines like this should have specific examples to aid in their definitions so we can criticize or agree with them. What could be considered "mean" to someone emotional/thin skinned, might be interpreted as helpful criticism to someone not so sensitive.

Sometimes it's really hard to say something respectfully negative (oxymoron), and even harder for it to be interpreted as respectful. I, for one, appreciate when people talk trash to me (especially when I'm wrong). It's an awakening I sometimes don't get from a less firm/colorful counterargument.