You're not being too smart here. If I had a "phobia" about this or was "judgmental," I'd say, "Family smooching on the lips is wrong and no one should do it!" Yeah, personally I think it's odd and likely unhealthy on different levels -- it's not how I, anyone I know or ever have seen, behaves. But I also accept that not everyone in America shares the same family customs and stated as much.
Also consider this regarding kissing children/grandchildren on the lips:
Some time ago Victoria Beckham posted a pic of her kissing her daughter Harper on the lips and wishing her happy birthday. It caused a heated discussion in the comments on whether it's acceptable or not. Doctors say, children must feel loved and safe in the family environment. But kissing on the...
brightside.me
Finally, I showed the below photo to a number of people and got the same reaction each time: "EWWW!!!"