Agree, people need to get a grip. My oldest is only in 1st grade so I haven't seen it yet, but it will come. My bil was guilty of this with his girls in AAU softball, it was embarrassing.
Grandparents can be just as bad. My daughters both have been in the club volleyball and school volleyball scene in DSM area and it can get beyond obnoxious. We've run into grandparents who act as childish as any of the dumb shouting parents, don't want to mention the school <coughJohnstoncough> but it's embarrassing.