I believe it because in all the epic trollings I've seen, there have been locals who have engaged with the trolls throughout. I can't remember the last time I saw a troll simply monologuing into the silent ether at length.

I also believe it because I've experienced people in real life who seem motivated by the desire to get a response from others, but who don't seem differentially motivated by different kinds of responses.

But, all of that said, I certainly agree that none of that is definitive. I could easily be wrong. And it doesn't matter too much for my own behavior... I mostly don't talk to trolls because I don't enjoy it.

If you are getting good results from talking to trolls, that's a fine reason to keep talking to them.