Why did Muawiyah (may Allah be pleased with him) kill the Companion Hujr ibn Adi (may Allah be pleased with him)?

There is disagreement regarding whether Hujr ibn Adi was a Companion or a Successor. Furthermore, Mu'awiyah (may Allah be pleased with him) did not kill him due to his verbal opposition, but rather because he resorted to actions, such as inciting people, reviling Mu'awiyah, and renouncing his obedience. Mu'awiyah based his decision to kill him on the Prophet's (peace and blessings be upon him) saying: "If someone comes to you while your affairs are united under one man, intending to split your staff or divide your community, then kill him." It is also mentioned that Mu'awiyah consulted people concerning his killing, and that his killing was based on his personal judgment (ijtihad) to unite the word and repel discord. Moreover, the conversation between Aisha and Mu'awiyah regarding Hujr's killing has been reported. Finally, one must refrain from delving into these events and follow the saying of Umar ibn Abd al-Aziz: "That was a tribulation from which Allah protected our swords, so let us protect our tongues from it."