What is the conflict between freemasons and knights of columbus?

Knghts of Columbus is a Catholic fraternity that requires its members to be catholics in good standing to join or remain members. However, Pope Paul XII created a policy of excommunicating catholics who belonged to secret societies one of which he declared was the freemasons. Nevertheless, freemasons and knights should not have any conflicts amongst themselves based on a technicallity just because that technicallity makes it impossible for someone to be both a freemason and a knight. So what are the real issues?