If someone is willing to patiently educate themself by reading posts on a tankie forum, that suggests that they are probably already interested in altering their worldview and are open to tankie positions, which is 90% of the battle.

But because our worldview is so demonized, most liberals don't want to be persuaded by it. It would be like, if one of us wandered into a highly detailed holocaust denial forum -- if we lacked the knowledge to argue back, because we're not nazis obsessed with denying the holocaust, that would be an uncomfortable feeling, and rather than opening our minds to this atrocious new perspective, we would hightail it out of there looking for someone, anyone, to debunk those claims (and in our case we'd be in luck).

The first thing to reach a liberal (or anyone) isn't evidence, it's credibility, which comes from our values, conduct, and epistemology. They first have to see that, despite what they hear and currently believe about us, we're good people, we care about the same things they do, and we try to inform ourselves in a rigorous, media-literate, open-minded way. Then they need to see liberal media as less credible -- it can help to start with low-hanging fruit, to establish that they do lie, at least sometimes. Then they're open to argument.

That can all happen pretty quickly during an interaction, even in the span of a few well-constructed comments. We have a few people who are great at this. But if someone is just minding their own business in other forums, absorbing the ambient anticommunism of their environment, they'll never reach that point, they'll never be curious enough to want to lurk or browse a tankie forum.