Whilst I still think the accusations of espionage and propaganda against the Confucius institutes is overblown, this is a definite indication the Chinese policy is moving to punish academics for pronouncements made outside the country. It appears that in the future not only out-and-out political enemies of the CCP, but also their serious critics in the world of academia are to be refused entry to the country in an effort to discourage such criticism.
Finally, we have this entirely disreputable and unworthy comment from "China expert" Shaun Rein on this subject:
"My guess more bloggers/ academics who froth [at the] mouth about China will be denied visas going forward."
Mr. Rein then went on to characterise anyone who found this comment objectionable as an "idiot/troll". Sigh.
As other commenters have already pointed out, if any other world power were to adopt a similar position virtually no serious foreign scholars would be allowed entry.
[Edit: Fixed links to individual tweets - for anyone wondering how to link to a tweet, just click on the "x hours/days ago" tag under the tweet and it will take you the tweet's URL]