I imagine because if you are going to make a polarizing claim like that, you should include a reputable citation, not require everyone who reads your comment to have to research whether it's true if they aren't familiar.
I thought it was big news a while back, but now it's old news. Not unimportant, but not the sort of thing that sounds so controversial that it must be cited every time.
Well, you don't necessarily need to cite it, but linking it to a real event and not an opinion by appending "as has been reported in the past" or even just "as we've seen" will take it from what appears to be a snide remark to the those ignorant of those events to something they may want to investigate further. It was just communicated more poorly than it could have been, and now we're all wasting our time on this rather than something more useful. :/