Icarly tickling question?

I am a mother of 3 two daughters 16, 13 and a son who is 8 and the other day I was watching the Brady Bunch i think it was Every Boy Does It Once or something away way in the middle of the episode Marcia and Jan started teasing Bobby about being short. The parents were siting right their and didn't do anything I thought how mean? Later in the episode they wanted to get some information from Cindy so Jan hung up her by her feet and Marcia started tickling her tell she told them what was going on. My husband said theirs nothing wrong with it my kids tease each and know teasing between siblings has been going on for years. But how come the parents did say anything when the Marcia and Jan were teasing their younger siblings Bobby and Cindy?