Kids these days

Last night my family had dinner at HEAT, and because the restaurant was packed, we were seated at a table inches away from the next table. Our neighbors were a father and his 2 daughters, who were around the ages of 13 to 15. The girls were very pretty, tisay, and spoke in heavy American accents, which led me to think that they were probably born and raised in the US because the dad spoke in a normal Filipino accent. Due to the proximity of our tables, I couldn't help but overhear their entire dinner conversation, which pretty much comprised of the girls talking to their dad in really bratty, obnoxious tones. The younger of the sisters kept bitching about how she'd been up since 3 that morning (doing God knows what), and that she still had a "shoot" the following day. The other girl had an exchange with her dad that went something like this:

Girl: Dad, will there be a car to bring me to the gym tomorrow? Because the driver will be with her [referring to her sister] all day.
Dad: I can bring you to the gym.
Girl (whining): But you're never there! Whenever I wake up in the morning you're not home yet. [from golf maybe?]
Dad (jokingly): Then wake up later. [I wanted to laugh out loud at this]
Girl (exasperated): Daaaaaaaad. You know I wake up every morning and go the the gym! [said in an anguished way that conveyed, "you're ruining my life"]

I can't remember the rest of what was said. I might have left the table on the pretext of getting something from the buffet just to get away from those insufferable, insolent brats. Someday if I have kids and they ever spoke to me like that, I would slap them. Seriously.

My siblings and I were taught never ever to raise our voices not only to our parents, but to any of our elders, including aunts and uncles, older cousins, and teachers. In our family, there is absolutely no excuse for such disrespectful behavior, and I have an extremely low tolerance level for it in others, even in strangers. Last night it took all my self-control not to glare reproachfully at the 2 impudent daughters for talking to their father (who seemed very good-natured too) in such a rude manner. I also had to resist the urge to lean over and ask the father, "Are you going to let them talk to you like that?", and instead fixed my gaze squarely on my plate, forking a piece of cheesecake and pretending I was stabbing the brats at the adjacent table.

Was it an overreaction on my part or is parenting nowadays so liberal as to allow children to talk back to their elders so impolitely? Should I lighten up and accept that this is how we're raising kids now, to be little independent and outspoken adults? Rather than be appalled by their brazenness, am I supposed to be amused at their precociousness? And if I feel like dumping the remnants of my DIY halo-halo over the head of a snotty bratinella, am I the one more deserving of admonition?