It really is an option. It really is the best option. It isn't flippant or sarcasm.
Facebook has done a sufficiently good job of intertwining itself into people's lives, so that to abandon it would mean losing touch with family and friends, missing out on invitations to events, excluding one's self from valued discussion groups and more.
What people resent is that Facebook seems to hold people to ransom like this, now they've made people so reliant on it.
So, sure, people can just leave, fine. But don't diminish the fact that for many people, quitting Facebook would have serious drawbacks.
If people don't like the way things are then they have to be the change. Facebook is not going to change as it's business model is based on selling it's users. In the absense of taking responsibility for themselves or Facebook chosing to change many default to arguements for government regulation. Bringing in the use of force like this creates problems significantly worse than the privacy issues of the original voluntary Facebook use.
But you just don't stimulate constructive discussions by asserting that the only rational path is the quitting, whilst not factoring in the costs.
This is not a simple case of "watching someone stick their hand on a hot stove and complain over and over that it hurts", because the alternative action you advocate just causes pain of a different kind.
Most of what you're saying is valid, except for the fact that it's simple and obvious to fix.
If it were that simple, we wouldn't need to have this discussion at all.