Give this person and yourself an "out." Tell him that no matter how much he pushes and begs, you will not, in any way, answer his question today or tomorrow. If he still wants the answer in two days, then he will have to very firmly state that he wants your answer and is willing and able to deal with any repercussions that may result. These are the rules and he must abide by them if he truly wants your answer. Any deviation and you walk away or change the subject permanently. He gets only one chance.
Having laid this overly-dramatic, but very serious, groundwork, tell him that you will be very blunt. You will remove all emotions and speak truth and only truth. And given that, this truth will be very difficult to hear. "You will not want to hear what I am going to say. Let me repeat, you will not be happy when you hear my truth."
"And so, it's up to you now. If you don't want to hear it, then just go on with your life and continue to be a friend. I'll not bring it up again. And if you bring it up after two days, I'll ignore you. I will assume that since you didn't take my rules seriously that you weren't really able and wanting to risk hearing my honest, unemotional opinion."
That's what I recommend. (Can you tell I've been through this before? More than once?)