You could kill the merchants, but other NPC's or creatures did not go into town/cities and kill merchants in any prior TES game.
i was about to call you all kool-aid drinkers and then this guy came in. good on ya.
regardless, i understand people will like/dislike the more "subjective" aspects of the dlc, such as story itself, but for anyone who doesn't see a problem with the random vampires spawning WITHIN the gates of every city, killing npc's (sometimes finding the bodies afterward, not even knowing there was an attack) with no real justification other than to provide a cheap, heavy-handed sense of urgency in pushing the player into the storyline, is just a bethesda apologist. tedium and repetitiveness does not add any "flavor" to the game, no matte how new the content.