They'd picked the wrong day to mess with Clive Felix.
Earlier that night, Clive had been hunting vampires in the heart of the city. A group of them were attacking people trying to convert more to their cause. Clive had readied his entire Anti-Vamp arsenal, and waited for even the smallest signs of vampiric activity. Nothing showed up, but Clive Felix heard about an attack on the other side of town. He had been wrong about where they would strike.
Hence, when the drunks started bothering him at the bar, Clive Felix was plenty ready to kick somebody's ass.