The thing is, to me Morris is 100% correct. The goal of any team in any sport is to perform better than their opponent on any given day. That leads to victories, and the ultimate accomplishment is to outplay your opponent in every single game. The Dolphins in 1972 did just that, and that can never be taken away from them, whether the Pats go undefeated or not.
Again, I think you're confusing 'undefeated' with 'best team'. The best teams in the history of the NFL, to most people, are some of the Steelers of the 70's, the '85 Bears, the '89 49ers, and some of the Cowboys teams. People discount the Dolphins because they had a very weak schedule and rarely dominated the way those aforementioned teams did. Does that take anything away from what was a perfect season? Absolutely not, and the best the Patriots can do, when it comes to the perfect season, is to be on the same 'undefeated' level that the 1972 Fins are on.