While you can explain to people what their means of redress are, you cannot tell people they can't complain, nor can you impose consequences when they complain about things that aren't illegal, immoral, unethical, etc. I have had people bring up things that aren't in the EEO realm as such (I.E. they just don't like their supervisor), and you can direct them to the appropriate means of redress.
Otherwise, I'm not sure what you're complaining about other than humans will behave like humans.
I think what any of us should be interested in - and perhaps what the new SD policy is about - are the reports that are filed fraudulently. I suspect this is extremely rare.
Edit: People just want to be heard, and if you don't create a command climate that fosters transparency, and a healthy means of feedback to leadership, then people are going to become frustrated and feel like the IG is their only option.