Force subsite to use: Users must be logged in to comment

Hi there,

I'm running a multisite based on a subdomain setup and I would like to make sure that all the subsites are being forces (or at least as default setting) to use this option in the Discussion Settings:
"Users must be registered and logged in to comment"

I'm experiencing a lot of spam whit this option:
"Comment author must fill out name and email" and I would like to either disable it or remove it the option completely.

Any way to make this happen?
Cheers,

Ronald