Problem is, liberals think declaring a general strike is a novel idea, as if the left hasn't been working towards that goal for decades - often times facing setbacks when unions are shattered by none other than the liberals.

As much as it is tempting to rip liberals up in a thread like this, these threads are a good opportunity to agitate. Outline how the entire left project revolves around building the organizing capacity to perform a general strike like this. Tell the liberals that the left has put A LOT of though and practice into this problem. Set them on the right path. Tell them straight up, "This isn't going to work. At least, not like this. Something like this requires a lot of groundwork, and here are the people who are leading the way."