Young couple goes on van tour of US, boy comes back with van - no girl

while it's notable that you want to protect your grandchild, i think your message is a bit convoluted
essentially you're saying "i don't have an issue with violence, i just don't want my kid to be the target"
and i think it's the violence/punishment dynamic that needs to be addressed no the 'identifying the proper target of violence' dynamic
Yeah, I wouldn't go as far, but I definitely would let them know in no uncertain terms that if there was ever any abuse, that my daughters would know that they don't have to put up with that and always have a way out in that case. The visceral response is totally understandable though.