But why should we give Tankies liberal fairness when they despise liberalism?

Because it's an important way that people who are confused by that tribalism can get un-confused. There is a strong impulse to "fight back" against the "enemies" or dunk on them, which I'm guilty of plenty of times, but also, I do think that being normal and reasonable with people helps to defuse that "all your enemies are Zionist neoliberal CIA NATO Hakeem Jeffries supporters" propaganda.

A big part of the .ml echo chamber is really emphasizing to each other what their opponents believe, so they won't have a chance to hear what the actual "enemy" point of view is and they won't believe it when they hear it. I think that is such an important part of the propaganda specifically because if they get to hear what the actual viewpoint is, it makes a lot more sense and undoes that "they are horrible and enemies on purpose because they hate you" worldview.

A lot of the "deprogramming" that you hear about from tribal identity comes from direct personal interaction with the enemies, and realizing that they are just people with sort of reasonable ways of looking at things. That's not what they were raised to believe about the enemies, it can be powerful to undo it.