There are reasonable consequence and there are unreasonable consequences. In Justine’s case, the tweet was a poor decision. But that doesn’t mean the reaction to it wasn’t wildly out of proportion with what she did. She made a stupid joke to her 147 or so followers. The consequences to her life wildly exceeded the harm she caused.
You’re arguing expectations. I don’t care. Is it ethical to attack someone like that? If not, don’t be part of the attack.
If someone stands in the middle of the road, they should expect to be hit by a car. But, still, I’m going to stop my car so that I don’t hit them. And anyone who doesn’t try to do the same, hiding under some argument of “expectations”, is doing something pretty shitty.