What’s the full command you are using or what are you trying to do?

It’s hard for anyone to help if you don’t give details, but I can only guess ……

The man page describes -r starting

If a file argument is a directory …

So, did you specify a directory?

Are you using the standard xattr command that’s built into macOS? IIRC there’s another program out there by the same name with completely different syntax. Try running type xattr; it should say something like “xattr is /usr/bin/xattr” if you’re using the standard one.