Get him drunk.
Kidding . . .
As near as I've been able to determine, the only cure for an out of control inner editor is time, experience and confidence.
The mantra I was taught by the head of a fairly successful workshop was: write, write, write, edit, edit, edit, submit, submit, submit. In that order. When you get something back, you turn around and resub it immediately. I can tell you from first hand experience that this formula works. I didn't think of myself as a writer until I started doing this. Rejections put hair on your chest

. Acceptances give you confidence.
This teacher suggested writing with your monitor off if you have to. I can't do that (I'm very visual and need the cue of seeing the words appear on the page), but I did find that writing flash fiction helped enormously. Sixty minutes of straight writing--a thousand words. Take a prompt and just go. This is tons of fun and one of the things you learn to do is trust your right brain for the story and puts you in authority over the left brain (the editor, if you prefer that term).
If you get good at it, you can even find a market for the stuff.