I spend some time trying to educate them
They generally appreciate it and occasionally check in with me with new openings even if they don't quite understand what the opening is for.
It definitely doesn't pay to slam them, although routing around them whenever possible is good. I also like to let them know I've figured out who their client is from their job description and make it clear that I'm still talking to them largely as a courtesy.
.....To the future or to the past, to a time when thought is free, when men are different from one another and do not live alone -- to a time when truth exists and what is done cannot be undone:
.....From the age of uniformity, from the age of solitude, from the age of Big Brother, from the age of doublethink -- greetings!
-- George Orwell, 1984