I don't think paleo rationalizes overeating per se. Some may assume this. However, it encourages eating paleo foods until you are full. Many people, when trying to be healthy, try to scrutinize every calorie and shy away from fat. In turn, they feel deprived most of the time.
Paleo, on the other hand, encourages nourishing you body instead of depriving it. In the SAD culture, eating until full or satisfied, especially if you are "dieting," is frowned upon. Compared to a SAD "dieter," a person following the paleo lifestyle would be grossly overeating fats.
Some people following the paleo lifestyle may go too far and give the impression that it's okay to go crazy and eat all the fat you possibly can. In reality, I think it really means that you should not deprive yourself of fats and foods that are taboo on SAD diets. Overeating on a regular basis, paleo foods or not, is hard on the body and the digestive system. Also, who feels like working out when you're always stuffed? Not me!