These would be the activists who are- as you call them- the instigators, and who might be close to the origin of the events. But the second level is the media- and here you have journalists and bloggers, who are already far removed from the original events and are supposed to report them to a wider audience in a neutral way. And yet you see them grossly misreporting the content of text they have read and that anyone can check: despite much less direct emotional involvement here (if there is any it should be acknowledged and balanced), and the fact that a news article takes much more effort and focus than a simple retweet.

So the justification for the spread of obviously false information can only be either an actual wilful dishonesty (and I don't believe it) or it's nothing else than a selective blindness driven by an instinctive desire to align to the immediate peers.