I think you forgot to explain how this guy is a scammer. You posted connections to several accounts that are alleged to be spammer.
Red trust doesn't always make someone a scammer, it shows that the person leaving the feedback doesn't trust the person recieving it. Lutpin has made his reasoning clear for the red mark in his feedback, as did Lauda.
Would you trust someone that spams and ban evades, along with little trustworthy things to their name?
Uh, yes, negative trust is meant for anyone who has scammed someone, who has attempted to scam someone, or who is believed to be a scammer:
Negative - You were scammed or you strongly believe that this person is a scammer.
The forum administration sometimes will allow someone to resume posting after being permanently banned after some amount of time has elapsed (depending on the amount of "trouble" the person previously caused), sometimes a new account is created, is allowed to continue posting, but the old account is not unbanned, and sometimes the old account(s) is unbanned.
None of the reasoning provided by either Lutpin nor Lauda give any insight to why the OP is a scammer, nor have they said anything along the lines of "trust me, this person is a scammer, but I cannot disclose how I know this" (this would only be used when someone is an alt of a scammer).
In addition, would you not consider somebody delivering a sub-par product for what you pay to be scamming? In that case, signature spamming and getting paid is scamming the owner.
Not in the OP's case, no (nor in the majority of other similar cases). It is my understanding that the OP was previously paid for a set number of posts made after an enrollment post (and/or enrollment time), made in a specific subset of sections, while wearing a specific signature until a specific time. Furthermore, it is my understanding that the OP was not paid until after he delivered his services, allowing the owner of the company he was advertising for to withhold payment if the quality of service was less then expected, which dilutes this kind of claim.