Yes, it's pretty unfortunate. I hope that they'll come to realize that they need more than conjecture. That goes for anyone, be it Mandiant, the US or other governments, etc. I'd much rather this be about real data, not just opinions and innuendo.
There's certainly a lot of bad traffic that comes from China, but the same is true of other countries. Show us why, don't just tell us, it is (or isn't) government sponsored, and why that's important so I can make the right security recommendations to protect the networks I'm responsible for.