What do you tell people who say that communism won't work because “people will corrupt it and take advantage of the system the same way they do on capitalism”?

"You're gonna shit, why ever wipe your ass?"

I just flip these stupid arguements on their head. There is no amount of logic that makes this make sense. Ask them this...if they think communism wouldn't work because "muh human nature" (which isn't even true, humans have only made it this far by banding together), then why does it make sense to keep the system that feeds into humanity's worst impulses?