Trailer would have been a lot more compelling if he had just killed her too, in some quick and somewhat humane way. If she was actually found "guilty" of something, then justice all around, but who knows, we haven't played that story out.
I don't think it's become fashionable to hate The Witcher, not in the same way it's fashionable to hate FFVII or ME3. The Witcher is a polarizing series for good reasons. I liked The Witcher 1 a lot, because it was a resurrection of the western CRPG during a period when they were dying off. It's combat was sorta inept, but playable and the characters were ok. The story was passable. In the end, though, it was fairly enjoyable.
The Witcher 2, however, was a total mess for me. Whereas a lot of RPG's, especially action RPGs, are starting to move away from "locked in town area where you randomly talk to everyone, get quests, go into wilderness, trek back to town" system that has been in place since... oh... before Baldur's Gate 1 I'm sure, The Witcher 2 continued that and it just felt old. The combat was ok, except the reliance an utterly inane potion system, which nearly required short term potions and, thus, short term ability to predict your upcoming combat. It was just stupid. The game felt tired and the systems felt sorta broken.
I know others loved it. That's great, I really hope one day I'll work up the interest to get back into it and finish it off, but I just can't bring myself to do so in the wake of many other games that I think just play better and are more interesting to boot. I know it's supposed to get better later in the game, but the first several hours were just too boring for words for me.
That's not fashionable hate, it's based on a lot of reasons, specific to my taste. A lot of people reasonably enjoy The Witcher, a lot don't, and, frankly, that's ok. (What's not ok is when the level of fanboy love or neigh-sayer butt-hurt ex-fanboy hate go into massive tirades lambasting anyone for giving a different opinion. For examples of that, I'm sure you can look to Mass Effect 3's haters or Halo's supporters. I'd say Half-Life's supporters (personally, I can't stand it) but that game's polish and competence are so high that at least those people's love is grounded in reality)