I've seen this a half-dozen times in online news in just the last 24 hours.
They say this as if it were impossible to question these events independently. No, of course if you have ideas like that, you're simply buying in to Russian propaganda! /s
Anyone now saying "I don't think assad did the Sarin gas" is now immediately associated with "you've fallen for Russian propaganda" in the minds of the people of America that eat up the mainstream media. Many will refuse to entertain the idea itself now, simply because "If I thought about that idea, I'd be entertaining Russian propaganda, and I'm smarter than that!" And another avenue of thought becomes closed due to a thought-terminating cliche.
Of course Russia has their own propaganda angles with every story, but an opinion doesn't suddenly become invalid because someone bad also said it... By that logic anti-smoking ads are pro-Hitler, because Hitler was anti-smoking.
That's not how ideas work. They can't just say "this is the only source of an idea, and if you have that idea, you're inherently tied to that source." as if it were impossible to think of an idea independently. As if independent logic didn't exist, and we were just all repeating the messages handed down to us by the media. Which is of course how the media would like to imagine its relationship with the public. I find this very telling.
It seems like we will see more of this. If the media doesn't want you to consider something, but the story is too open to simply ignore, they will put out "Russians say that..." stories about it everywhere. I think we'll see this tactic more and more.
The cold war is over, but it seems like the media wishes to restart it...