"Walk in the light, or we will drag you to it."-Subjugate others to follow their religion? Evil. At least Harkon banishes you from the castle. The Dawnguard on the other hand are very bad, have you see their torture chamber? The room which holds irons and burning sticks and macabre tools of torture surrounded by blood? They kill and torture vampires out of hatred for the unnatural.
Vampires kill people for the sake of food. If they feed, the sun is staved off. Apex predators kill only what they need to survive.