Why does brotherhood of steel want to kill the player after killing Danse

It doesn't make any sense. Danse is a synth. The brotherhood of steel came to Commonwealth to destroy the institute and synths. There is no trial, player can never explain his actions and brotherhood is instantly hostile. Surely even when they found Danse's body they would notice synth implants during autopsy. Player did them a service by removing a double agent. Idk I think the brotherhood should actually provide an immediate offer to the player to join them along with some benefits.