When Facebook’s ad network sells and places ads in front of a person because they are gay, pregnant, devout, or disabled, you don’t consider those to be “intimate details of their lives”?
Facebook has a giant ontology of subjects. Based on their "stalking" of you, subjects in this ontology are connected to the user profile; i.e., the FB user's "interests".
Ad buyers are buying access to the ontology, not the individual users. They're not given a list of users to sift through and choose the user. They choose the subjects and FB's ad network shows the ad to users with matching interests. For what it's worth there's at least a buffer there.
You may still find this wrong, but the idea that they're providing "intimate details of their lives" oversells the argument against FB.
BTW: you have to at least give FB credit for giving users access to the interests that are tied to their profiles. I periodically sweep through them so that I show 0 interests and subsequently never get any ads. Ad buyers are looking to target people; if you're not in the target audience you wont be shown an ad.
I consider all of those to be intimate details of their lives. I cannot purchase that information from Facebook.
What makes this more confusing and frustrating is that there are companies that do sell user data to Facebook. Not in the handwave-y, roundabout way people that OP describes, but in the standard "I give you $$$, you give me transaction data" way.