Explain in your own words how Jason justifies his new marriage. Do you find his arguments convincing?

No, Jason is rather a slimeball. Jason and his family were exiled from his native kingdom of Iolcus. Here in Corinth, Jason has gone behind Medea's back and taken another bride. He is depicted as an opportunistic and unscrupulous man, full of self-deception and repugnant smugness. He condescends to his wife, although she is in every way superior to him.