Here's a situation that may happen. You go to a new organization for a few meetings with some friends. You don't like it, and stop going. A few months later that organization makes donation to an questionable charity. That charity it actually a front for a terrorist organization. So now the organization you went to but no longer are a member is now funding a terrorist organization. The FBI does a search of members of the organization and find that you attended a meetings. Guess what. Now you are a terrorist and you can now loose your citizenship.