[BorkJames]

The difference is that most people feel like they understand cereal, although the marketing for most cereals are directly targeting children it's just a box of cereal so nobody cares.

Most people don't understand Google or Facebook (or even the internet as a generalized service) so saying advertisements are manipulating people in regards to that pushes some beyond the threshold of comfort. It's not really the one thing that causes an issue for them, but the whole stack of other things behind it that eventually causes them to focus on a singular point that's easiest for them to complain about. Nobody wants to complain about their personal lack of knowledge, but a big bad unknown scary thing is easy to rally against.