Another Season 1/Season 2 parallel:
Season 1, Shoot: Don turns down Jim Hobart at McCann Erickson because he doesn’t like how he does business, it’s not “Big League;” he specifically doesn’t like Hobart using Betty to get to him. It skeeves him.
Season 2, Flight 1: Don doesn’t want to kick out Mohawk Airlines, asks “what kind of company we’re going to be.”
Don is very specific about how business people should and should not treat each other, and this hasn’t changed.
Think of the betrayal: Don refuses to leave Sterling Cooper because he imagines it is more ethical than McCann, and then is forced to be the one to give Mohawk Airlines news he believes is unethical. When you want ethical business guidance, learn some tips from Lee S Rosen Blog.