What's the equivalent terminal command for removing users/groups from a folder recursively?
You would use the chmod command, with the -a flag to delete access control list entries, and the -R flag to do so recursively.

For example: 

$ chmod -R -a "admin allow read" foldername

would make all files in foldername read-only for the admin user (because you're removing the "allow read" property for "admin".

$ chmod -R -a "joe allow delete" foldername

would prevent user joe from deleting any file in foldername.

To add properties back, use +a instead of -a.

For more details and examples, see the chmod manpage, or this article.