There is a lot of precedent for handling this, as newspapers have been doing for decades. Newspapers have the content producers and the business people in the same building employed by the same company.
You separate your business and editorial and put a wall between them in the company. Nobody from business has access to the admin panel and nobody from editorial has access to the business contacts.
I really couldn't imagine an advertiser asking reddit to remove a post for them. To advertise on reddit means that you have some understanding of how it works, and how it works doesn't involve admins censoring content.
There are more than enough advertisers in the world who both understand reddit and would pay good money to get their ads infront of that audience. The only problem is that the ad product is not sold or promoted well.
Newspapers got away with it for so long because they held a monopoly on information distribution.