The fact that FBI agents are forbidden from speaking to the press shows that they have something to hide. If the email investigation was conducted without bias, then the FBI should have nothing to fear by letting agents speak with members of the press. The gag order shows though, that the FBI thinks that an agent may reveal incriminating evidence against Ms. Clinton, and that would contradict with their ruling.
Many believe that Hillary Clinton is hiding something about her emails. The FBI gag order indicates that Hillary is likely hiding something from the public. Therefore, the public should demand that the Justice Department get to the bottom of whatever it is that Hillary is withholding. Also, if the Justice Department refuses to hold Clinton accountable, then the voters should in November.
I think it needs to be done. They didn't find anything that was really "bad". It could be that the gag order is to prevent any more leaks or compromise of any confidential information. Agents basically signed something reminding them not to disclose sensitive information or to discuss the investigation. May not be open and transparent behavior, but hardly the diabolical picture the conspiracy theorists are painting.
The gag order which is believed to be a inside deal is not an indication that Hillary Clinton is hiding something. It may have been put in place to protect her against those who may want to use the email saga to turnish her presidential ambitions. But as it seems even the FBI knows who they want to be the president.