General Dempsey has many offical duties, all centering around the military defense of the United States. He certainly has no role in advising private citizens as to the content of their political speech (if you regard Jones's speech as political) or their religious speech (if you regard it as religious) or the free expression of their idiocy (which is probably what it is.)
If Dempsey had made this call on his own time and his own dime, and without further publicity, it would possibly be justifiable; but to do it apparently in his official capacity (announced by his spokesman) is clearly an attempt to use the prestige and authority of his office to have a "chilling effect" on civilian speech.
We can incline towards Dempsey's point of view while still seeing that he is abusing his position.
The fact that it was publicized shows that he hopes that his efforts will extend beyong chilling Jones, to chilling everybody.
Jones's idiocy has nothing to do with it. Dempsey's efforts are incipient tyranny.
Given his position and power I don’t think even a private call on his own time would be appropriate.