Yeah, treating people differently due to some arbitrary out-of-control factor (e.g. age) is always wrong in my books.
Hamilton is probably a weird example to reference, though. He's spent his whole life being on the end of all manners of passive and active, selected and systematic and direct and indirect racism from primarily an older crowd (at least within the industry). He's probably entitled to hit back after what's happened recently with Piquet and Ecclestone.
Saying that when he says 'older', I'm not sure he's referring to old as in age, more so as in perspective. That is people who have an outdated viewpoint rather than people who happen to be beyond middle age.