John was so disappointed in his wife after he found out that she had been cheating on her diet the entire time, that he did not visit his father. Instead, he called off the hit and went to talk to Tony, informing him that he will accept Ralph's apology.

After he went to great lengths to try and defend her honor -while mentioning how hard his wife tries to lose weight- John caught Ginny with all that candy and realized that the problem wasn't Ralph's joke, but Ginny's inability to give up the sweets.

As for why he protected Paulie, like another poster said, John didn't want to give up his mole. Paulie's big mouth was making NY some money (and costing Tony his). Who knows what Tony would have done to silence Paulie if ever he found out he was the one gossiping.

Badabing! wrote:..., John didn't want to give up his mole. ...

That's the first time i realized the "coincidence" about the word 'mole' (Paulie = mole). The joke was about the mole on Ginny's a$$. Classic Sopranos!