In the early years of ads on facebook they had targeted ads in the sidebar, but the news feed was left untouched. One change that happened is that Likes started giving pages access to space in your feed. Eventually pages that I didn't explicitly like started gaining access there. After that the algorithm for ordering the feed changed (probably more than once).
I was okay with the targeted ads in the sidebar, when that's all it was. I opted not to block ads on facebook with adblock plus. I learned of all sorts of products that I probably never would have heard of had I been getting random ads, or ads intended to appeal to a wide audience. I never felt manipulated.
The tweaking of the news feed feels wrong though even without ads. Maybe it was an inevitable result of the quest for profits, but if I could go back to targeted ads the way they used to be, I would do it in a heartbeat.
The reality is that I've been fed targeted ads all my life, but the targeting wasn't was optimized. Automotive magazines are more likely to have ads for spark plugs than hair products. A cooking website is more likely to have ads for spatulas than tractors. At least, that's how it used to be. With ads fed from Google, ads are likely to be related to what I've recently searched for with their search engine. The result is often comical: I no longer see ads relevant to what I'm interested in at the time, but to what I was interested in 30 minutes ago. I'm not clicking any of those ads; I've already moved on.