There's another reason too: defense against cognitive dissonance. If it's one's "own team" that did something bad, and that person is unwilling to give up allegiance to their team, they will often act out in other ways to resolve the conflict. Especially since the partisan aspect of the issue is not headlined, the defenses will be similarly under the surface.
I flagged this story and comments like this is why. If you want to argue the pros and cons of a government policy, do so. Reading accusations of astroturfing etc is not intellectually gratifying.
