Fair enough. My experience is that contract recruiters will not even pass pre-screen candidates that they "hear negative scuttlebutt about". I understand it, they want to send candidates with what they think are the most likely to be hired, and my experience is that the recruiters understanding of "likely" may unconsciously bias them.

Employed on site recruiters you can have a good conversation with and say "Even if you hear they are not good, if they check the boxes on where we're looking I would like to review." Which, given they are evaluated by candidates delivered rather than candidates hired, works out.