He didn't. He said "er, umm... Let's not do that any more, OK?"
"Fuck no" would have included timely investigation and prosecution.
Much as we on the left would like to, there's basically nothing to give Obama an attaboy for.
I guess that prosecuting Bush and Cheney (Not to mention Tenet, Rumsfeld, and the rest of the bums) would have been 'inappropriate'. I suppose they could have arranged a sham 'Reagan Party' at the Hague and let the europeans capture and prosecute them as the war criminals they are. Sadly, I suspect that that would have started a somewhat one-sided "WWIII".
So, really, there is nothing we can do. However, a recent OP-Ed in the NYT made the case for a presidential pardon for everybody involved, because if Obama doesn't somehow recognize that this was a crime, it could happen again. Putting Bush in jail would be best, but it will never happen. Making him a pardoned felon could have some effect on future presidents.
And, I'm not even sure Bush understood what was going on. Cheney, yes. That guy is Darth Vader. Tenet? Yes. Rumsfeld? Yes. All those guys would be in jail in a perfect world.