Thinking about this more … I think what would really turn readers/viewers off about the “kill the dog” moment is if they sense that the author felt it was okay to do that. So maybe:
- If you truly do feel like it wasn’t wrong to kill the dog, make sure you get the why of that across to the audience. (This might be what you’re going for with the “benefit of everyone”, or maybe not, maybe that’s just a mitigating factor.) And I guess, make sure you represent the alternate viewpoint too.
- If you agree with what most people’s initial reaction would be, that killing the dog was a reprehensible act, then make sure you don’t make it seem like the author is okay with it (even if the MC is).
I guess your position might be more nuanced, but I think the idea holds that you don’t want the audience to get the wrong idea – you want to communicate your position (possibly through other characters).
Note I thought of this going over some feedback on a story of my own, where I may have overly-excused the IC’s behaviour in some spots, especially from the MC’s POV. Writing the draft, I fell a little in love with the IC myself, blinding me to some of the terrible things she did (though strangely, not in the scenes that were from her POV!). I hope I’m not wrong in applying the same concept to your character.