It's certainly true that all we can do today is speculate about how this new immunity will be abused, but I suspect we'll find out a lot sooner than we'd like.

Its fair to approach arguments like this with skepticism because they sound so ridiculous, but I think they're lent more credence when referenced as a concern in the dissent from the Supreme Court itself. Sotomayor said: "When he uses his official powers in any way, under the majority’s reasoning, he now will be insulated from criminal prosecution. Orders the Navy’s Seal Team 6 to assassinate a political rival? Immune."

If you want to say she is worried over impossibilities too that's fine but based on the facts of the case and how it was ruled, I don't see why its not a realistic concern.