Isn't Cambridge Analytica enough proof that harm has been done by Facebook's data collection and allowing others to access it? That's the very tip of the iceberg.
For me, everything is about, that it could be harmful. And that's true it could be. Lots of things could be harmful. But right now, it's not really provable by anyone that it is. What we need is proper laws to control what companies can do. And in some areas of the world we're getting them. They're not great but like all tbings they will improve.
But it seems very much like there is an attitude like working for Facebook or Google is amoral. That I don't believe. Especially when there are companies sell software to track phones secretly to countries like Iran. That's on the border of amoral.
It was used to figure out which parties were most susceptible to being manipulated with misinformation and outright lies so that they would vote for people whom would ultimately harm their own interests. For example figuring out which groups of liberals could be pushed towards a third party candidate with propaganda so that that a conservative candidate could win the election and disadvantage the same folks. This is straightforward harm even if the election was still technically democratic it was swayed by manipulation partially funded by our enemies and those who aligned themselves with Americas enemies to get a president elected by the minority to harm the interests of the majority in order to enrich a much smaller minority.