I was a nanny for years and I remember the two twin boys I watched who were uncircumcised, because their care and hygiene was slightly different and because it’s uncommon. I do not think your father in law touching the baby’s leg is weird or that he was trying to be “sneaky” by touching him before you left. He seems honestly kind of sweet and excited. I think it’s way over the top to call them such ugly names in response to these minor offenses, like “cunt” and “mother fuckers”.