Remove Blog registration fields when register with Facebook

I have the option "Both sites and user accounts can be registered." active on my multisite with buddypress. And I would like to remove the option to create a Blog when people using "Register with facebook"

I already have removed the option from the normal register page by editing the register.php with the buddypress templates. But I dont know how to do this for Register with Facebook without changing the option "Both sites and user accounts can be registered."

Any advice?