Delete on my iMac, but not on my Mini

Hi all,

I'm trying to free up some space on my iMac, so I want to delete the movies I have in iTunes- easy enough, and I know that they'll stay in iCloud. But when I go to delete them, I get a warning box stating that they'll be deleted on all devices connected through my iCloud account. I have a Mac Mini with all of my movies stored, and I don't want the movies to be automatically deleted on the Mini. Any way to just delete them from one and not other? All software and OS's are the latest versions.

Thanks.

John