Blade is technically a half vampire, so I say Blade-like heroes can be a part of this jam.Vampires kill each other all the time, but they are rarely represented as mindless creatures like zombies. When they kill each other is for matter of politics, power, or love.
The rule basically means "give players a vague motivation for killing vampires, don't make it a mere power fantasy". How you interpret it is up to you!
Also this jam doesn't have judges, so I can't really stop you from disregarding the rules anyway. Go on. Live your best life. Rebelling to society is part of being a vampire, after all.