How to add_filter/action to comment out CSS generated by admin function?

I think you can do it like this:

function my_admin_bar_init() {
    remove_action('wp_head', '_admin_bar_bump_cb');
}
add_action('admin_bar_init', 'my_admin_bar_init');

Add this to your functions.php file. It will disable outputting of these inline styles in <head> section but the wp_admin_bar will be still available.

If you would like to disable wp_admin_bar entirely, you can do it like this:

remove_action( 'wp_footer', 'wp_admin_bar_render', 1000 );