Obviously, they aren't creating wealth--so objectivists have no reason to like them. Deceptive business practices are a form of coercement--it cuts to the heart of "contracts," the idea that people can only form business deals knowingly and willingly within a civil society. So most objectivists believe they have the right to take action against telemarketers, and generally limit themselves to what is legal because it's not worth going to jail over (it would only be immoral to walk into a telemarketing firm's HQ and blow away all of the top management because you would go to jail, and that would be too selfless).
That's my take on it, at least. I guess I will have to defer to your much more knowledgeable, nuanced, and fair understanding of objectivism that you are charitable enough to share with us all.
Gubermint, get off their backs, now!
If it wasn't for government protecting them, there wouldn't be any telemarketers, they would all have lead poisoning.