The definitions of of good and evil are way to subjective to begin with, which makes the argument difficult unless those words have a set definition to base an argument around. If we assume good as a positive action or positive result, then only opinion of good that matters is the actor and the recipients of the results. I think that will always be subjective. Evil I think is a poor word to use as it indicates the nature of intent, which can very from person to person with the same action. Bad is a better word I think, but cause we can assume it to be a negative result. The negative can be determined through and examination if harm is done through the action. Then the next question that comes is the circumstances surrounding the harm to see if a wrong was committed. Since doing harm can be justified, like defending yourself against an attacker, or demolishing your old home to build a new one. But then what justifies harm. You could get as many answers to that question as there are people to ask, but I think it can be worked if we can agree each life belongs to the one that experiences it. This does only work though if we accept that we are conscious, self aware and can act under our own will. If you do accept that you area self aware, its not a large step to assume other humans are self aware. Since our self is the only will that can experience the life each of us individually go through, no one can own a life other then the one they experience. I think from there you can determine whether a harm is justified or not among honest and thinking people. Which will then move into whether or not a harm, and what degree of harm, should be done even though it may be justified, which would be based on the values of the individual, which moves back to a subjective nature.
everything is subjective. e.g I can fat shame someone and through tough love they will change their ways and improve their lives. for some fat shaming is bad. In this case is good.
Is it good? What about emotional harm, possible destruction of a persons belief in their own self worth? How about a distorted perspective of body image? Sure, they my exercise, eat better, loose weight, but what if their idea of self worth is not based around their weight now? Believing if someone else believes they are over weight, their value as a person is less? You would hope that some one would be emotionally strong enough to over come such cruelty, but what is being at a healthier weight better if their ideas of self worth is damaged in such a way? Then if they were abused in such a way to cause them to loose weight, could that not then continue the cycle of abuse with that person then fat shaming others? It is the potential when one uses harm to curb another's behavior. But it really comes down to my point. Your justification to do harm to another was to change their life to how you think it would be best. But who are you to make that decision for someone else? It is their life, not yours, and by doing harm to their life, not to protect your own, but to conform their life to your will, you are in effect taking a position of ownership over that other life. I believe no one should attempt to own another, so your justification is false and the potential unintentional consequences (hoping they're unintentional) could far exceed any benefit they might gain from eating better(possibly worse) and exercising. This doesn't seem like good to me. The only justification for the harm comes from a subjective opinion, but based on incorrect or insufficient reasoning. Which makes the subjective position wrong and the value of the action bad.