There's a reason people are more comfortable about insulting people based on age: everyone either has been or will be a member of the class they're criticizing.  People who want to complain about a group without getting in trouble seem to often try to position themselves as part of or close to the group before complaining about the group.<p>"My girlfriend or wife is [group], and I can tell you..."<p>"I was in a gang when I was a young man, and let me tell you..."<p>"My brother is an IT guy, and so I can say that..."<p>With age-related remarks, no one needs to even posture.  There's an implicit "...and I can say this because I'm one of them, or will be".