and of course on the regional boards there is every likelihood of the WhiteKnight/s  meeting the lady.

BTW it's a lot more likely on many boards for the WhiteKnights to "be the mob" not the other way around. It certainly keeps a lot of guys from posting honest reviews or reporting NCNS out of the quite realistic fear of some BSC Hooker and her legions of White Knights ganging up on him, so they simply keep their mouths shut.

I don't understand their function. Do providers give discounts to white knights? Are there other incentives?

So we are all talking about the same thing.

that if they defend the honor of a lady then that lady will think better of them and perhaps lend them consideration or fall for them somehow.  No matter that the girl has no idea who you are, or even perhaps despises you, the white knight thinks that somehow fighting for the reputation or hand of the lady is its own reward sometimes.  You see it everywhere on the internet.

...that this will ultimately lead to better sessions, or does he worry that his action-- say an unflattering review-- will end up with the provider giving him less personal service?

your judgment gets clouded or you think it's the best opportunity to make an impression.

Now, I can get laid by my provider whenever I want.

And then post up the most inane garbage in an attempt to deflect the reality that their favorite gal is indeed a bullshit artist.

White Knights were raised by single moms who brow beat them into a lifetime of subjugation from all females. They are acutely sensitive to all matters of sexism and objectification toward women, yet they openly laugh at jokes based on men’s ability to take out the garbage or dispose of “bugs” found in and around the house, or men's innability to ask for directions. White Knights are fervently against breast augmentation surgery as well as most other cosmetic surgeries and treatments, deeming them all humiliating, dehumanizing and dangerous. White Knights choose their P4P partners for their loquacious and narcissistic personal website biographies rather than any classic standard of beauty or libertine service menu.

Make pudding, and place anklets on their destrier.

I'll see if Taylor can drop off a check when she's in NYC...or maybe Courtney.

But the thrust of your OP should discuss things like.....

I saw a provider a few times who has a White Knight on one of the regional forums. If anyone says anything bad about her, he's posting to the rescue immediately.  

Sometimes "White Knights" or other reasonable people object to seeing people ganging up on and bullying other people on the Internet.  There seems to develop a pack mentality when going after what is viewed as a vulnerable person (with or without reason, there is often no explaining it).  

I am guessing it doesn't say "2labman" living on the TER boards in Anytown USA.

What is the psychology of the typical asshole demeaning the few women who are good enough to provide such a valuable service to us? Who are they helping? On some level their logic is probably to hurt their self-esteem and their business, resulting in lower rates. That's the only conceivable advantage that can be gained from it. It's seems like they're trying to hurt their feelings so bad that they leave the business. It's dumb, just like calling girls sluts all the time then complaining when a chick won't sleep with you because she doesn't want to be "thought of like that". Fair is fair and some providers may deserve it but often it's just some jackass acting like a insecure little boy on a playground. I won't put up with them on a message board or IRL.