I agree that you should be assuming your fellow writers should be/are doing their best. However, it doesn't free you or anyone else from criticism (preferably constructive criticism). You and others are obviously entitled to your own opinions, which may or may not be positive in regards to the character/writing/etc. You may think something is dark, but another person might think it is just edgy. Killing an innocent witness, as mentioned in your example, could easily be taken as a "haha, look how evil my character is", hence the fine line I had spoke in my previous reply. Describing your character as an "asshole murder hobo" probably isn't helping your cause as well, given the context of the terminology used.