In our defense, older people don't travel well. We're just not as portable as we used to be. And we have an early bedtime - we get grumpy when we get tired. Travel combined with a late hour in an older person is a lethal mixture. Crashfrog's job brings him in contact with older people at their worst.
Speak for yourself. Some of us old farts have been grumpy old men since we were teenagers. I travel a lot (mostly international, which is even worse), and haven't noticed being any more grumpy afterwards than beforehand. OTOH, I can't imagine anyone who isn't already on the list for a rest home for the terminally stupid - of any age - who would tweak ANY salesperson's nose in a store. No matter how cute the salesperson might be. That's taking condescension to pathological extremes, IMO.
My only irritation with the "younger set" comes from dealing with a certain subspecies of that ilk. Percy, I'm sure you know the type: the salesclerk in the computer store or wherever who treats a certain age group (like, anyone over 30) as being already senile and ready for assisted living. I usually lose my temper and say something along the lines of "A) it's not the years, it's the mileage, Junior. And B) I already know more about this sh*t than you in your dead-end, minimum-wage job will ever learn. Now show me the two pieces of hardware I asked for or get someone who can." For some reason, I never get any discounts in those places...