BuddyPress.org

No, you wouldn’t have to do any of that running around. If that theme is only used on that blog and you have it turned off for all other blogs except the home blog on your site, then you just have to drop this into functions.php for that theme.

remove_action( 'wp_footer', 'bp_core_admin_bar' );

remove_action( 'wp_head', 'bp_core_add_css' );

In that theme the admin bar won’t show. Ever. If you use that theme on other blogs then you’ll have to wrap those two calls in some code to detect what blog it’s running on and only make those calls on blog id 1.

You could also create a plugin that runs in /mu-plugins, use those two calls above and just detect what blog it’s running on and make the calls only for blog id 1. That might be better.