Lizard for Sale!
It seems weird that a Buy/Sell/Trade group on Facebook wouldn’t allow the buying, selling, or trading of a particular object. However, if that object is something that’s totally banned in the group, and if it was stated in a pinned post, then the group’s members can’t do anything about it, right?

That’s right. And Facebook won’t interfere, unless what a group’s admins are doing is illegal, which, in this case, isn’t. So, Karen, threaten all you want to get the admins hauled off to Facebook jail. Nobody wants to buy your BF’s dang lizards. Accept the fact that your for-sale posts will continue to get deleted.