This isn't truly extortion or blackmail here, as has been mentioned, but I would suggest that mdayonliner probably shouldn't be putting those kinds of terms on feedback removal--if you tag someone for merit abuse, scamming, or whatever, you should do it for the good of the community and my opinion is that unless you made an error, the feedback should stick. Even if it's untrusted.
Mdayonliner isn't benefiting from any of this, even if these people are giving him neutral feedbacks. That doesn't get him anything, and that's why I'm saying it's not extortion or blackmail. Others may have a different opinion.
OP, your name sounds familiar. Did I remove a neg from you in the past?
Edit:
Nope - you have never given me a neg.
I often post in scam posts and have done some projects with Cryptodevil.
Ah, OK. I know I know you from somewhere around these parts. Anyway, it's untrusted feedback and I know you're not worried about it. If this was a DT member, all hell would've broken loose already I'm sure. This isn't going to affect the other members involved much either, unless they have very thin skin.