Using GMail while advocating breaking up some anti-competitive/monopolistic practices/companies isn't hypocrisy.
It's using a singular product to do what that singular product doe; which is fine. I can advocate Johnson and Johnson be fined for anti-competitive practices and still buy a stupid band-aid without abandoning my morals. Why would an email provider be any different?
Perhaps someone trying to radically change the way company X does business, in ways the leaders of said business aren't going to like... shouldn't store (or even transmit) their private correspondence about it using the services of the company.
I mean, that would _normally_ be common sense. Seems weird to even have to point this out.
Before she can fulfill ant campaign promises like that, her campaign email will have fulfilled its purpose, anyway. So even if that were a likely outcome, I don't see why it would be a concern.
In any case, care to elaborate?