Sorry, I’m still not sure if I follow exactly what is the trouble here.
Its true the short-code [rml_read_more] will put a login form in your post. This form will only be visible when users are not logged in, as you may have observed. The text below the short-code will be hidden, and user needs to log in to read that text. That is the main purpose of this plugin.
Also keep in mind the plugin will redirect the standard WordPress login/logout, register and password links to a pages as specified by the plugin’s settings. In these pages you can put additional plugin short-codes for membership handling, or you can put your own stuff here. This redirect will be active as long as the plugin is activated. In case you don’t want this redirect, you need to deactivate the plugin.