[dude with glasses in a communist t-shirt, arguing] I'm the only leftist here, your opinions are TRASH
[dude holding a theory book on smug, arguing] Read theory you losers, you're all WRONG
[dude in an anarchist hoodie, arguing] Nuh-uh, I'm the only leftist here, you're SHITLIBS
[the three dudes are now caught in a cartoon fight, glasses gone flying, punches everywhere, while a firing squad of nazis are targeting them with rifles]
[a confused nazi asks] Why… why are they still arguing?
Under capitalism you can criticize capitalism. under communism, dissension is met with punishment.
If not death, or being institutionalised.
But you can also get institutionalised or killed under capitalism too if you say the wrong things (China, Russia, the Gulf States).
While you might not be killed in the US, but you can be harassed via lawsuits or deported to a foreign internment camp if you say the wrong things.