There are plenty of ways of being critical of something without being inflammatory. In your earlier post, which I assume is this one[0], from the banned account called "wastebook", you refer to everyone who uses Facebook as "narcissistic", imply that they're liars, and state they have no "real friends". That's a massively wide brushstroke to use given the size of Facebook's userbase, and doesn't lead to constructive discussion.

The worst part is that it undermines your own point, which is a shame, because when put more sensibly it could actually be reasonable: your argument, once you strip out the vitriol, is that social media is reducing the ability of modern people to nurture deep interpersonal relationships. That's the kind of opinion that can lead to a good discussion, with points to be made on either side, but it's impossible to have that discussion if you start it by pre-emptively insulting everyone who would disagree with you.

I can absolutely understand why the mods would choose to immediately ban you, given that it was an insulting comment, the first comment on a new account, and an account which, based on the username, appears to be crafted for the sole purpose of disseminating those insults. All that is enough to ban you, and you don't have to run to the flimsy assertion that your comments on Hacker News are going to be affecting Facebook's stock prices.

[0] https://news.ycombinator.com/item?id=8852896

Edit: For the record, the comment that was deleted was a comment from a throwaway account "warning" people that anyone who would post anything negative about Facebook would get their account hellbanned because "pg and other YCombinator investors have plenty of facebook stock". By the time I hit the "submit" button it had already been deleted. Pardon me for falling into the temptation of feeding the troll, but I felt I could make an interesting point.