You accuse them of being a socialist because they support Biden. Then you run through all the thought terminating cliches:
- Human nature
- Imagine you have 2 cows
- Totalitarianism/authoritarianism
- Socialists are just utopian idealists who haven't received their first paycheck/don't know how the real world works
- Explain the origin of money using the barter myth
- Climate change related thought terminating cliches that could literally fill the character limit 3 times over
- Call them a tankie
- Say that tankies always claim real communism has never been tried because they keep moving the goalposts
- Show them the reddit front page, /r/theleftcantmeme, etc whatever you can to make the brand of lib you're portraying look as uncool as possible
Then you show them your power level. Make them feel as frustrated as we feel when we speak with their cracker treatbrains. At the very least, from then on if you talk with that person ever again they'll have to think twice before they say some stupid thing you could easily dismiss as sounding like the character you cooked up.
Also, I guess this is just the standard-issue wrecker strategy that some trolls use against us here, ended up recreating that unintentionally 
Liberals agree with most Libertarian talking points
If they agree, you just treat it as a rant instead of an argument. Rant about tankies and commiserate, then hit them with the "every single word I've said since we met was a fabrication."
It will probably fail because we would reflexively tried to present a coherent argument instead of just wildly flapping their gums as libertarians usually do.
Well you can make it a gradual thing where you start out talking about the invisible hand of the free market, and as your conversation unveils more and more contradictions of capitalism you start talking to them about social and productive forces, the tendency for the rate of profit to fall, imperialism, etc. Then once it feels right you admit you were taking the piss initially.
You could also do this with a libertarian but instead of an argument it would be a "discussion" where you outline the points and understand it better than them and then announce the ruse.
