How inappropriate was this comment and what does it indicate?

My husband and I have been best friends with another married couple for 15 years. The other couples wife was always obese, I have always been thin. Recently the obese wife went on a huge diet and lost a bunch of weight. Her husband said to my husband that his wife now looks better than me in a bikini. He was watching his wife from inside the house getting into jacuzzi in the back yard and called my husband to come over and watch with him he also asked my husband if he appreciated looking at his friends new thinner wife while she was getting into the jacuzzi.

I think it's wonderful that he is so happy about his wife's weight loss and doesn't notice all the loose skin but why insult your friends wife? In all the years of our friendship my husband has never said to his friend that is wife is the best looking.

I'd like to know why.