I think Director Comey didn't like being called corrupt as the Donald Trump campaign and House Republicans did after the previous statements about the Clinton emails. 

With this announcement the Trump campaign and House Republicans can no longer say the FBI is corrupt. 

Director Comey is making a statement regarding the Clinton emails when the country believes everything about the campaign is corrupt/rigged and charges of gunmen were found to be not guilty. I think there is a valid concern about retaliation by gunmen after the election in 11 days.