mmm I think the bigger problem with that scene is the fact that littlefinger is built up in the books as an extremely cunning, almost visionary person who can play the game like a chessboard, but when he's convicted of treason his rebuttals are:
"i'm a bit confused"
"none of you were there"
and "please sansa i've only protected you"
the show has always failed to make littlefinger appear as tactful as he is in the books, with precedent leading all the way back to season 1, the first time you see dialogue between littlefinger and cersei. littlefinger randomly says this inflammatory thing to cersei, showing that a) he wants her power and b) he isn't to be trusted, and cersei just fires back with this one-liner that renders him speechless. book lf would have done his best to both brown-nose as much as possible and avoid altercations with more powerful people he's trying to control.
it's been shit like this that turned me off from the show, leading all the way back to the first season. it needs to be said, though, that the first few seasons are MILES ahead of the last few from following book narratives to overall quality