And indeed, as Dutchbat and the entire Yugoslav conflict illustrates, they are HIGHLY selective in what justice they provide. Or the most recent Israel situation: every country in the world gets to decide WHO on their soil can get prosecuted for war crimes. That's part of the ICC charter. Except of course Israel doesn't. Palestine, however, does gets to dictate who doesn't get prosecuted, on the exact same territory. ICC doesn't enforce it's membership agreements against Mongolia, or South Africa where it comes to Putin. And so on.
ICC shows everything wrong with the world, and the UN: they're powerless, but promise (I should say "sell") the world. They are an excuse for governments to do nothing. They are highly paid totally ineffective politicians. They are corrupt. They are racist. They let themselves be hired for shouting real loudly at ... whoever you want, really. Sometimes it's even someone who deserves it (like Putin), but mostly it's not. They're behind the times. They are not independent (e.g. not throwing out Mongolia for hosting Putin against the Rome statute or South Africa for very publicly violating the Rome statute and publicly promising to do it again (about Sudan and Putin). They're not independent in legal matters, often publicly cooperating with political maneuvering between countries. And to top it off, they fuck up security in email server.
They are an offensive affront in so many ways. They are offensive to the idea of justice. They're offensive to good government. They're offensive to international agreements (or at least to the idea of actually following agreed international agreements). Hell, they're offensive to good computer security practices.