PoE bitching on here has more to do with many on the board reacting to the game like their wife cheated on them than anything to do specifically with the game.
It's a butthurt sense of betrayal that Obsidian of all developers made such a bland game and they're constantly chewing the scenery over their beloved ones dropping the ball when they were meant deliver the perfect RPG that would save the genre (and possibly gaming as a whole).
It's the worst kind of hype-backlash and fanboyism that prevents this forgettable game from being forgotten.
It doesn't change the valid points the likes of Sensuki make about the game, it's just that they keep doing it like that ex-husband ranting to everyone over how much of a bitch his wife was to him and how he can see everything wrong about her looking back on the relationship.
Many of the most vocal critics were not only Obsidian fans, but had put their money on the line for them during Kickstarter. That plus the amount of effort many Obsidian fans spent to help the game succeed, whether by being in the Beta, vouching for it on forums, etc., resulted in the backlash. This is, I suppose, one of the risks with being crowd funded - hell hath no fury as a fanboy scorned.
As to why Sawyer is targeted, and not Fenstermaker, Avellone, etc., it's because he kept a high profile and was responsible for most of the design decisions that people knew about. Fensternmaker actually does deserve a larger share of the blame/praise than he's given, but people don't know him well enough to say what he actually did, and he isn't a very public person with hundreds of quotes across different forums, interviews, etc.
Besides which, even though a lot of the talk now is about Pillars of Eternity's failures in plot, setting, and characters, during Beta and around the time of release, the bulk of the talk was about systems & mechanics, which was Sawyer's work. As an example, just look at early negative Codex reviews such as:
http://www.rpgcodex.net/content.php?id=9867 from DarthRoxor
http://www.rpgcodex.net/forums/inde...illars-of-eternity-very-minor-spoilers.98295/ from felipepepe
You'll see that all but a few paragraphs of it were dedicated to criticizing the class & combat systems.
Sure, we've had long threads about the writing in the game since then, but it's not been on the same level as the amount of attention people initially gave to the systems side of the game. Sensuki, DarthRoxor, felipepepe, and others all concentrated on the systems, and that's Sawyer, and so Sawyer has become synonymous with all that was wrong in Pillars of Eternity, even though a lot of the problems with the game's story & setting weren't due to him.