I hate telemarketing calls - but I try not to take it out on the telemarketer. I just remind them that I'm on the federal and state do-not-call lists, I'm not interested in whatever they're selling, please don't call me again. If they keep going on I just hang up (quietly - I don't slam the receiver down).
The do-not-call list doesn't prevent charitable organizations from calling. When they call, I tell them to send me something in the mail and I'll review it. I won't commit to a dollar amount on the phone, nor will I give out my credit card number on the phone if I did not place the call (duh!).
I also have a rule: If I'm eating, the call goes to voice mail.
It's ironic: As I was posting this, I got a call from a telemarketer. At the touch of a button, I sent him to voicemail. No message, naturally. I love my privacy manager.