I agree, and I feel like that goes for everything in general. It's like people who get mad at customer service people - the customer service person has absolutely nothing to do with the product that's giving you grief. Even the telemarketer, as you point out, doesn't want to be there (or even if they do, they may just be there because they have no better options and need to put food on the table).

In life, there are very few situations where being unkind is ever worth it.

And even here on HN, I sometimes get the impulse to argue with someone for whatever they said. What I do is I type out my little comment, then close the tab without actually posting it. Some things are better left unsaid, regardless of how satisfying they'd be to say.