Indeed, you just stood here. As you sat there drinking while they drained a human in plain sight.

[ The body lies still on the table, blood dripping sluggishly from its neck. Spock does not need to look over to it to know it is a corpse when there is no echo of a third heartbeat or sounds of another person breathing. The vampires abandoned their food easily when it came to saving their lives. ]

You are a vampire. That is reason enough to consider you an enemy.