Nobody is obligated to accept being treated badly. People should draw the line when that happens. The rarity of tanks simply means it's far more noticeable when they do so. It's absolutely the right thing to do. There's no grand conspiracy of tanks who think they're extra special, it's just a lot of individuals who've decided they don't enjoy tanking in LFR. I'm sure DPS and healers have decided the same, it's just not as noticable because there's more of them.
I do disagree with your basic argument that it happens equally though, my experience is that tanking comes with higher expectations in terms of gearing and preparation, and that there's an expectation tanks will somehow pick up the slack of the rest of the raid and anger directed at them when it doesn't happen, and often anger directed at them when they don't really understand what has actually happened but want someone to blame (the number of times I've seen people go off at Monk tanks for gemming crit this patch is obscene). It's not the entire raid that does those things usually, but all it takes is one moron to ruin the experience for the tank and make them decide not to try again.
You say it's a people problem, but doesn't that also mean there's a people solution? The community could do a lot more in taking an active role in reporting/kicking those people and creating a less shitty atmosphere. They appear to have chosen not to do so, and in that case can't really complain that there's suddenly a lack of punching bags for them to take their shit out on imo.