Your example is one where the advertisers are charged to sell products, but the humans they advertise to curse them all the way. My proposal is one where the end consumers alone decide the worth of a post. If money is paid by end users, they were pleased to see the content.
It makes no sense to say that this incentivizes advertising. An advertiser could already post in a forum - FOR FREE - and there is no reason to complicate things by adding a mechanism by which people could pay them to advertise. It also makes no sense that anyone would pay the advertiser to advertise. The advertiser is also not going to pay himself.
While there are certainly going to be negative outcome use cases, the administrator at the end of the day is still the decision maker about when certain types of content are going to be allowed.