We will have to agree to disagree. I don't think it's a good failsafe to tell someone that is a teammate that we will murder you all the while you are instructing them to do everything in their power to save Daisy. If the situation were reversed and it was Lincoln possessed and Daisy wanted to go, I don't think Coulson would ever have suggested that.
So unless you think he would have forced Daisy to wear a murder vest, it was a morally bankrupt decision that he made simply because he values Lincoln's life less. If it were Daisy, we both know she would have insisted on going and Coulson would either insisted she stay behind or would have taken other precautions that didn't involve the murder vest. If there were no other precautions he could think of then he would most likely let her go and have himself or May stick close to her.