ב"ה I know the Rambam states that one must not ever get angry as ChAzal have also warned of its dangers which I agree with. But certain situations arise where a person needs to be stern or even confrontational at times to get people to get things done. I am aware of sefirah of gevurah, but everytime I am stern, I usually feel really bad. How does Judaism look at being stern with people, is it looked down upon or a necessary evil so to speak?
Rambam himself addresses this. He writes in Hilkhot De'ot (2:6) that although one should avoid anger, should the need for sternness arise, one should feign the emotions, while remaining cool, calm, and collected:
וכן הכעס, דעה רעה היא עד למאוד; וראוי לאדם שיתרחק ממנה עד הקצה האחר, וילמד עצמו שלא יכעוס, ואפילו על דבר שראוי לכעוס עליו. ואם רצה להטיל אימה על בניו ובני ביתו, או על הציבור אם היה פרנס, ורצה לכעוס עליהם, כדי שיחזרו למוטב--יראה עצמו בפניהם שהוא כועס כדי לייסרם, ותהיה דעתו מיושבת בינו לבין עצמו, כאדם שהוא מידמה איש בשעת כעסו, והוא אינו כועס.
And so to anger is an extremely negative character trait, and it is proper for a person to distance himself from it to the opposite extreme, and he should train himself to not get angry, and even on something that it is normal to get angry over. And should he want to impose fear on his children or household, or on the community, were he a communal leader, and he should he want to get angry at them so that they return to the proper way, he should make himself appear to them as though he is angry in order to chastise them, but inside he should remain calm, like a person who is imitating an angry person, but is himself not angry. (Translation my own)
His son Rabbenu Avraham, similarly writes (HaMaspik L'ovdey Hashem ed. Wincelberg page 71) that anger is always inappropriate; even when it would seem normal in circumstances. External sternness however, is sometimes necessary. In fact, he writes that one [such as a ruler] who must administer punishment and does so with pure intentions and not out of anger is on a level of piety close to that of prophecy.
Evidently, sternness is not only sometimes warranted, but in cases where it is, if it is with pure intentions, it is appropriate and praiseworthy.