we got a lot smarter when our kids were about 21.
We had no name calling, but like Knot's kid, you could TELL they thought we were dumb and REALLY REALLY uncool.
Poor kid used to walk 10 feet behind us so people wouldn't notice that those dorks (us) were his parents.

it's really hard to control what your kids say to each other when you're not there. You have to take the little one aside
and explain that the older kid has this "disease" called the teen years, and you can explain about the attitude and how it's only temporary and one day the older one will be kind again.