Social Interaction

Are parents responsible for the behavior of their grown children?
You are invited to friends for dinner. A grown son or daughter of the hosts is at the table. He/she speaks in strident, dismissive and belligerent tones. The hosts pander to the son/daughter, while you feel exceedingly uncomfortable. You try a change of subject, hoping the offspring will not enter the conversation, but he/she continues the attack mode.
What are the social expectations of a) the hosts and b) the guests in such a situation? I would love to hear your thoughts on this.
At Slideshare, I found (and agree with) the following information: www.slideshare.net/.../guiding-social-behaviors - United States.