Tell him there is a one word answer----MOVE. We don't stop people from leaving.
You know, that worked with one of the lefties I encounter on a frequent basis.
One day shortly after the election they were going on and on about their spouse wanting to move to Canada, How could they live through 4 more years of GWB. I said well then, if this is such a terrible place - please do go to Canada and stop whining about it. I didn't much like WJC but I never made empty threats about leaving during the 8 long years of his tenure.
They haven't brought up politics since.