Evil itself is always bad, regardless of consequences.
Intent > Action > Consequence
If the intent and/or action are evil, or lacking good, the consequence is irrelevant. No one gets into a car accident and goes "Well, my mom died, but at least I don't have to put her in a nursing home or pay car insurance anymore." To define evil as anything other than bad would be like saying darkness can sometimes be light. And the analogy connection there is that while both ideas need each other to contrast and thus be identified, it doesn't mean they are interchangeable. If anything, making them or their products interchangeable would disrupt the meaning. Good itself cannot be evil, nor can good acts, though the consequence can be viewed as "bad" or "unfortunate" if it was not viewed as beneficial or in accordance with moral good.
Example: a surgeon intends to save a patient's life (good) and performs life saving surgery (good) but the patient dies (bad or evil outcome). Why would we believe that the intent and action were possibly evil because of the consequence? Medicine is a good in that it allows people to aid and save lives. But people can be allergic and it can kill people. Is it thus evil? Was the medicine itself evil for being an instrument of an evil outcome, even though the intent and action was essentially good in nature?
No, that doesn't make any sense. And neither does the idea of evil being "good" sometimes. Now, it may be your point that evil can inadvertantly cause some good, but this isn't a philosophical revelation or a reason to reevaluate the notion of evil; it's just the way things happen. Consider this: I drop a coin of Fate. It will cause a chain of reactions that will eventually either war or peace, an outcome which I cannot predict nor affect. If I drop the coin, and it causes peace, does that determine that my intent was to cause peace? No. Because of all the variables in life, we cannot determine 100% all outcomes. Therefore the outcome of an action should not determine its nature as good or bad, but the action and intent should, which we DO have control over.
Anyways, the nature of consequences does not preclude objective morality and prove consequentialism.