| Quote #4
Jason: were you [Medea] living at the world's ends,
Jason seems to think that his having made Medea famous somehow makes his betrayal OK. However, Medea never demonstrates the same need for fame that Jason finds so valuable. This weakens his argument greatly
| Quote #5
Jason: I wanted above all
Jason doesn't seem to see his actions as a betrayal at all. He contends that the only reason he married Creon's daughter, was to provide his family, including Medea, with a better life. This is probably his most credible argument, though the idea is alien to most modern audiences.
| Quote #6
Medea: Go, my sons, into the halls of wealth;
Medea could be seen as a traitor as well. She's purposely involving her sons in a plot which will make everybody in Corinth want to kill them. You might say that her betrayal is far worse than Jason's.