@cammerhammer
While i do think you bring up an interesting point, you need to remember that said bully already had "permanently" altered another person's skills(stats?) . I would say this is more along the lines of doing to him what he did to others.
Since the bully clearly knew what he was doing. And did so with no signs of sympathy or regret for his target until someone stronger appeared (and even then he only acted and spoke out of self inrerest). I would say this is completely justifiable as a result.
Actions have consequences. Power requires responsibility. If you abuse said power on others who are weaker, someone more powerful than you will use theirs on you, either for justice or for their own satisfaction.
One thing to think about is whether in this world, if it is more natural for the stronger/smarter to take advantage of the weaker because they can. Whether society's social structure is built off of an individual's power/intelligence as a requirement or if it is by popular social groups and/or nobility who decide the fate of others. My bet os it is that while society has a social structure determined by the populace and run by nobility, one's strength and intelligence are actually still the final say. In other words, if you are powerful or smart enough, you dont need to conform to society.