It was posted by some campaign-person. When she personally tweets something, it is followed by a --Hillary.
But the campaign person is going with the ethos of the candidate.
It's something the DNC's doubling down on with their ad about how it's wrong for Republicans to criticize radical Islam.
The main argument on political correctness is that Democrats and liberals are unwilling to discuss things that are true (which is necessary for coming up with solutions) because they're worried about causing offense. And we have the DNC outraged that Republicans are saying something that is true (Radical Islam is a problem) because it might cause offense. This seems to be a litmus test for the Clinton campaign.