The reply to this is an absolute banger

I'm using liberal in the sense that many leftists who annoy me do, to describe anyone who's not truly right wing but disagrees with them on something.

I'll also that that a lot of what other leftists (and to lesser extent you) say hinges on the assumption that most modern liberals are well versed in politics and are loyal to liberalism. I agree that many people who identify as liberal would probably actually be further left if given more information, especially if it's not in the condescending way that many leftists are wont to do.

I don't fully agree with you about Sanders. I may be wrong but he strikes me as somebody who is in favour of socialism, but knowing that he can't achieve socialism in short time, is trying to be pragmatic. He won't manage to create a world ruled by the workers in his lifetime but he makes efforts to improve the lives of workers within this one.

I don't believe that we could or even should attempt to throw out the system and institute a socialist one in one motion, we have to transition from one to the other. An attempt to transition too quickly would almost certainly lead to another outcome like the USSR or CCP.

Finally, I just get frustrated that so many leftists seem to act like liberals are the real enemy, and that anyone they disagree with is a liberal who must be purged from the ranks. Liberals share some socialist ideals, and it is more effective to cooperate over what we can agree on for the time being.

Point bounced right off their head. Just the perfect demonstration of the differences you outlined between liberal idealism and socialist materialism. They even give their own interpretation of how a liberal revolution ought to happen, totally divorced from history or theory, so we don't end up with another "bad" outcome.