Firstly you've contradicted yourself - you say you were banned 'just for being on this site' then go on to say you were banned with 'no explanation'. So how can you be sure about your reason for being banned?
Secondly, like many other sites which are free, they have the right to remove anyone, for whatever reason, or no reason if they so wish. Such sites take a great deal of time to manage, especially when there is no financial reward for doing so. As a former Mod here I know how much time I spent trying to keep things running smoothly, and can only guess how much time a full admin role requires. Indeed when asked if I was interested in assisting the admin of Local Ads, I was quick to point out that I didn't relish performing that sort of role again, nor did I have the time to do so anyway.
There are many people on Local Ads selling items both there and here on the Org - it's quite easy to spot them as the text and pictures are usually the same - so I refuse to believe you were removed for that reason only. I also don't think that removing the site (if that is even possible - so long as they're not breaking Facebook's rules) is warranted as most who use it have only praise for the admin of those pages and the way they are run.
Also , whenever I've felt there to be an issue, I have raised it with the admin of the group by PM (not openly as many seem to prefer or think appropriate) and there's never been any indication that they are anything other than grateful for the feedback.
You mention 'victimisation for passing on decent information', but maybe what you consider to be decent and what the site admin thinks differs, or maybe it's more about the way you passed on the information, but I very much doubt your ban was for the reasons you gave.