Hah. So it's ok to be ageist but not sexist? Think about why you don't see 'parents' as ageist...
This is the problem with today's politically correct climate - it's not about what the person is intending to say anymore, it's about how people perceive what is said. And if a group perceives it as offensive then look out, because it doesn't matter what your intentions were anymore because your intentions are now being decided by others for you. Any hypocrisy in those people's stances is obviously to be ignored.
It's an interesting dynamic to watch. It's a shame you have to tip toe so much, it almost seems to take away from the actual issues these days.