force login loophole

It seems to me that all you should need is this:

function force_login_wpse_89581() {
  if (!is_user_logged_in()) wp_safe_redirect(wp_login_url());
}
add_action('template_redirect','force_login_wpse_89581');

That should force users to the login page except for users who have already logged in.

I don’t know what bells and whistles those plugins provide that my solution does not. Maybe you need something more complex.