It's not about citing heinous cases. You're solving for a different aspect of the problem. Bastard Dave was convicted via an existing enforcement mechanism that in that case was at least arguably functional. The point is if Bastard Dave were a UN peacekeeper in central Africa, the host nation would be unable to try the case, and the UN itself mostly grants its own people blanket immunity and wouldn't prosecute it, either.

The rest is a different conversation.