Why is the acted-upon in sodomy killed just as the perpetrator is killed?

The Companions unanimously agreed on executing the sodomite, based on the Prophet's (PBUH) saying: "If you find anyone doing the deed of the people of Lut, kill the one who does it and the one to whom it is done." However, they differed on the method of execution, including burning, throwing from a high place followed by stoning, or stoning to death.

As for punishing the one to whom it is done (the passive party), it is because he is a partner in the transgression, and its corruption is immense, and because his remaining alive would lead to great corruption. However, if he was coerced, there is no punishment for him, according to the Prophet's (PBUH) saying: "Indeed, Allah has forgiven my Ummah for mistakes, forgetfulness, and what they are coerced into."