Show and book Stannis are both self-righteous, stubborn, and incapable of any kind of compromises, which proves to be their undoing. Stannis has always been all about using any means necessary to get what is rightfully his, no matter the cost or how others would feel about it. So burninating Shireen is just the logical next step (he already burned his in-law and tried to burn his bastard nephew). Sure, he is not that desperate yet in the books, but who knows what will yet happen... except the people who have a direct line to Gurm?
As long as TWOW is not out, screaming about "character assassination" is pointless. We do not know the particulars of how and why Shireen will be burned in the books, only that she most certainly will because the fat man told so to D&D&D. Now, it may be that Stannis will win the Battle of Ice but will still lose the Battle of Winterfell and in his desperation orders Melly to burn Shireen. For all we know, a raven bearing these very words might have caused the commotion that leads to "For the Watch" in the books (if the Queen's Men, including ser Patrek, intend to burn Shireen, the wildlings and Wun Wun might rustle their jimmies a bit). Or it may be that Melly will burn Shireen on her own initiative in order to resurrect Stannis whom she thinks to have died as stated in the Pink Letter (absent from the show), whether true or not. But as long as we do not know, let's just wait.
However, pulling a "JR shot at the mirror instead of himself" would be a cheap trick as far as Stannis's fate is concerned.
I think people take the things characters say about Stannis for granted while he has shown himself to be far more compromising and less rigid than thought. He even has a sense of humour. Plus he would never burn his own daughter, not in the books, he sends out Ser Justin Massey with the specific order to make Shireen queen if he falls in the upcoming battle. What Melisandre and Selyse are doing at the Wall with Shireen, that's a whole different story.
http://www.reddit.com/r/asoiaf/comments/39wt32/spoilers_all_relax_the_upcoming_battle_in_twow/This is a very good read about what might happen to Stannis in the next book. Personally I'm also a fan of the theory that Stannis will be Lord Commander nr. 1000. After he has lost all, he goes there. No lands, no glory, no wife, no kids.