I can confirm that having ennemies sometime goes hostile don't fail the achievement.
I followed this guide :
And contrary to this guy, I didn't get as often as him the smooth operator bonus which made me though I had failed the achievement (I was doing the e-books, hard difficulty and pacifist at the same time and said to myself I would do another playthrough without doing the sidequests in easy mode to get "Foxiest of the hounds" but I got it when I finished the game (I heard an alarm once but I reloaded the game and never failed any computers hacks).
So I don't think the smooth operator is really needed, you can probably never get it and still get the achievement. The achievement description just talks about alarm, not the other things.