Why do some women hate men's ex-wives?

I think the former and the present are two opposing relationships. One represents your past and the other represents your present. Moreover, women are naturally jealous, and it is reasonable to hate their husbands' ex-wives.

My brother has been married twice. His current husband is usually very knowledgeable, but he has shown a very tough attitude towards his ex-wife. He believes that since two people are separated, they should not contact each other again. Even if they get along well and have become strangers, they should not appear in their respective lives.