I would do as some of the others suggest and ask him to refrain from correcting your grammar period.
That being said, I'm trying to break my husband's bad grammar habits, he and his entire family say 'Seen it...' as in "I seen it at the mall" or "I seen it yesterday". He had no idea it is a misuse of grammar as his entire family uses it, I just don't want our kids to adopt the phrase. I've pointed it out to him and he is trying but sometimes he lets it slip and I'll remind him but not in front of other people.