What you are failing to understand is this happened in a comic book. Sure its impossible to actually hold a black hole let alone get anywhere near one but who cares? This is Superman here, if he wants to hold a fukin black hole with his pinky finger he will god dammit. I might think to myself "what the fuk, IMPOSSIBLE!!!". This don't change the fact he did it and oh yea... ITS NOT REAL.
Im confused as to why u ask if its rational or not as incase i have not made my self clear, it is fiction, it does not have to be rational.