Do you know in this age anyone in USA who doesn't have access to the Internet and also would want it? I never met anyone, like that. I met people who don't have Internet (usually older people), but they are also not interested to have it.
Even if there are such people in US, they can get Internet access in library (together with free books and free newspapers), because surely they also won't be able to afford a computer.
Of course, due to the people I associate with, I don't know anybody without access to internet. But I knew quite a few people at school who didn't have access to internet at home.
There's a lot of parts of the world where there aren't libraries with publicly accessible computers.
Some Internet with strings is better than none. But, some types of Internet with strings is better than other types of Internet with strings.
It's easy in a position of privilege (as the vast majority of HN'ers are), to say that it's an absolute wrong for FB to offer free internet (with whatever that entails).
But if you're a poor kid in a dead end community, and the only way you're going to get internet, and something that nears reliable access to information (whether it be learning to program or whatever) is through FB and their 'free' internet, you'd be jumping for the FB internet. It could offer you a unique opportunity to bootstrap yourself out of your situation.
It's similar to how you get free radio broadcasts, or free newspapers, or even free books. You can still learn and gain information from them, and they all have their bias and propaganda.
Freedom isn't a binary thing.