Mammele – While I hear your point, I do think that politeness is more important. As a telemarketer, it really upset me on the rare occasions when someone hung up on me. I have to say that this was very rare – probably because I was calling Frum people for Frum mosdos.
If someone is giving a long speech, I can hear interrupting them politely to tell them that you can’t give, but it should be done politely as opposed to just mumbling something and hanging up ubruptly.
If you think about the fact that this person could be your neighbor or friend, then you would act differently than if you think of them as a nameless annoying telemarketer.