>(I am never rude to telemarketers other than the ones who won't take "no thank you" for an answer. And even then I just hang up. They're only doing a job, albeit a crummy one).
That's what they're counting on, that you'll be polite to a stranger, but then that's premeditated and, well, telemarketing is rude by definition. Laws were made to ban the door-to-door peddlers, and telemarketing is just a way to bypass the door.
My last skirmish with one of them was last week, when I started with "wait, wait, do we know each other? Then why are you calling me?" and she went on with "oh, come on, stop acting on me", to which I agreed, "alright, I will stop acting" and started yelling at her.