We have separate domain admin accounts other than our computer logins. This is good security practice. This way when we are logged into our pc’s and happen to walk away and forget to lock the screen noone can use our accounts to do anything nefarious. But I have to tell you our technology manager has a domain admin login id as well. You may not be able to convince him not to have domain admin rights, but perhaps you can give him a separate domain admin id. It really depends on how active a role he takes in making changes or if his role solely delegates those responsibilities to his employees. I have had both as managers. The one who took no active role did not insist on having domain admin rights, but my current manager does.