None of the articles I read said anything about this only being ads. Ads are either approved or rejected by people, not censored. So could you state your source of information of it being ads?
I've found it difficult to find information on exactly how this s working. I'll give you the basis for my guess:
* Most of the conservative political posts on my Facebook page are sponsored postings, not things individuals have posted. Take a look at Facebook yourself. A fairly large chunk of what's there is really ads -- sponsored postings. It's not normally traditional ads, i.e. things advertising products, though some of it is. Much of it is political or religious, including non-profits, and much of it is from perfectly reasonable sources.
* Around the election, controversies about Facebook policies were about political ads, not censoring individual posts
* It's hard to see how 18 people could be the source of much of the information without using ads. To my knowledge there's no one an individual can post to large numbers of people without using the ad mechanism.
I would be interested to see any solid information on exactly how this is happening.