My daughter already has a mom, and she is AMAZING. I am not attempting to replace my daughter's mother's role by being our daughter's primary caregiver. I am her dad. Did I mention that I have an AMAZING wife that is NOT the father of our child? Would you call my wife "Mrs. Dad" because she works 40 hours a week? Of course not. "Mr. Mom" is just as ridiculous. Dads are parents too. We can be every bit as nurturing and caring as mothers when given the same amount of training and time with our children. There are thousands of men who are the primary caretakers of their children, and they probably don't want you to call them "Mr. Mom" either. Just go ahead and eliminate the phrase from your vocabulary.
Greg Jennings doesn't want to be called "Mr. Mom" either.