I am really trying to understand the other side here, so please help me out on this one. Let's say you have two people for the sake of simplicity, we can call them Alice and Bob. Alice and Bob hate each other's guts, Alice is unwilling to work on the team if Bob stays on the team, but Bob is willing to work on the team regardless of Alice. Furthermore, Bob has already worthwhile contributions under his belt, whereas Alice has done nothing yet, but she might if Bob were to be remove.
And your choice would be to remove Bob from the team. Am I correct so far? What sense does it make to remove someone who 1) has already a proven track- record and 2) has shown that he is willing to control his emotions to focus on the task, all in the hopes that 3) the other person might perhaps fill in the void and 4) already has show to let emotions override work duty, and 5) has a track-record of wanting people remove from the project? Please explain to me how kicking Bob out of the team is supposed to improve the project. I am really trying hard to wrap my head around the issue, but this logic is entirely alien to me. Wouldn't it make more sense to just tell people to keep any personal grudges out of the workplace and carry on? It is not that the project management is preventing Alice from joining, she refuses out of her own volition.
