Of the generals around him, Flynn is obviously worrying.  But Flynn is hated within the defense and security establishment.  (It was at DIA where the grunts came up with the term "Flynn Facts".)

Bigger issue is Trump clearly sees no need to listen to any of the competent generals around him.  Mattis and others are apparently on the verge of resigning.

That said, I should add a qualifier to my comment:

On the list of groups to worry about, the military ranks quite low.

Be nice to America. Or we'll bring democracy to your country.