They've said they intend to hunt down and punish informants named in the Wikileaks docs, and they have a long enough history of brutality towards informants (as you'd expect of any side in a military conflict) that it's only prudent to take them seriously.
But sure, let's all sit behind the safety of our computer screen in our (relatively) free and democratic society, and scoff at the possibility that this might make the struggle yet more difficult for people fighting for a chance at freedom and democracy in their own land.
But we haven't. So until someone shows that they have been killed, I presume that they haven't. That doesn't mean that it won't happen in the future.
Still, it'll hardly embolden anyone who might've been considering becoming an informant.
So, fair enough of you to presume no killings have eventuated _yet_, but it's a diversion from the main point: you can't call it a step forward in the struggle for freedom and democracy in Afghanistan.