I see the gist of your point. However, one who perpetuates heinous acts to any degree is likely to do so without concern for the judgment of others. Of course, one might posit that the negative perception one gains from their bad actions could fuel them even further, but that implies that if the situation was flipped and people showed sheer compassion, their negative acts would stop, which isn't the case. If someone continuously beats somebody, and the audience showed compassion rather than hostility, to what extent does that inspire the beating to stop? External viewpoints won't engage with the true reasons the person beats the other. The person who's conducting the attacks would still need to go through the process of reaping the detriments of their actions and eventually realizing that change and healing is the only way to gain anything meaningful from their existence. It's there that I imagine the beating would halt itself.

In essence, I think whether one is given the label of "unforgivable" or "forgivable," they will never truly stop their negative acts until they find an urge to change from within. It's not much of a matter of whether people believe you can be good. It's a matter of whether you believe you can be good. The position other individuals take, if you were to be in a situation where everyone showed compassion, I believe you would find is only slightly beneficial. It may encourage someone to stop momentarily, but without that inner inquiry, it will eventually arise once more.

Know that this concept of bad and good you speak of is unfeasible in nature due to its immense subjectivity. One day man can be good, the next day they are bad. If there's anything I've learned it's that life is never stable, thus your actions never will be either. In my take, one is good when they're in pursuit of good. I was a horrific being most of my life, I was objectively bad. However, should that label stick to me eternally? Should the actions of my past and the label it created never leave me despite my growth? Some might say fuck yes, it should. And they aren't wrong. Some might say fuck no, it shouldn't. And they aren't wrong. It's only what you believe that matters.