Perhaps one day we (society) come to the conclusion that advertising, as a whole, is doing more harm than good and we decide to ban it entirely. Or we decide set a limit on how much advertising is allowed.
Right now adblockers are not against the law (afaik) so I don't see any problem using them. After all, they're a product of the somewhat free market that facebook is part of and they accepted the market price (which is that some people choose to block ads).
I'm not arguing that Facebook isn't allowed to try to stop adblocking. Only question is what means they're allowed to take. Just like security guard isn't allowed to shoot shoplifters on sight.
Ads are like a donation box, not like a price tag.
Am I being forced to donate?
Well, you're certainly entitled to your own opinion. But realistically, we all consume content that is ad-supported that we might be paying for otherwise. The fact that so many ad-or-pay services exist is proof of this (Youtube with ads, Hulu with ads, etc.) The are both business models.
If you don't like the service at the price, don't buy it. Honestly, no one is forcing you and tons of people get on perfectly fine without Facebook (some people would even say they are better off without it).
The fact of the matter is, most people waxing poetic here about ads infringing on their rights, will still use Facebook when their adblockers don't work. They are willing to pay, they just want to pay less.
This is a very hard position to justify ethically.