Tait was a proud Mormon, and the minute Carl started getting nasty, it was over. He could have offered Tait $100 million, and he still wouldn't have taken it. There was no way he could work for Carl again.
Ethan Lock, from what I understand, isn't really a bad guy. But I'm not sure he and Carl have had many negotiations since that incident, and both of them -- at least during that escapade -- were vicious toward each other.