The text was too small for me to read easily in your link, so I just sampled it.

I suppose it depends on what you mean by public-- my handy example is that Trent Lott's political career was destroyed (severely damaged?) because he made a racist comment.

ETA: And even his comment was mild compared to what people say when prejudice is considered the default.

Hard to tell from this. Facebook and Twitter exist in an odd kind of limbo where they're treated as somewhere between public and private depending on how wide someone's network is, how sensitive their life is to dumb crap they might say online, and how aware they are of online privacy issues, so the stuff that crosses your feed isn't necessarily representative of what the people behind it might stand behind in a more traditional environment.

Then there's contextual issues. The linked image clearly isn't a conversation, or even a time slice of a hashtag somebody's following -- it's out of chronological order and any replies aren't shown, so it doesn't tell us much about how representative this is of opinion in general or about how people usually respond to opinions like these, both of which are important when trying to gauge public acceptability.