How I believe the Durkula awareness reveal will go.

[Gusion]

In English, "reasonable" is also used to mean "not excessive". Killing someone for lying is unreasonable in that it is excessive. Killing someone simply for being powered by negative energy is similarly excessive.

A being of wholly negative energy that is shown to be lying about who/what they are. We simply disagree if it is reasonable or not. Which is fine, there are very few circumstances in the universe in which everyone would agree it is okay to destroy anything.

Anything true of all Evil creatures is still true of Evil vampires. All Evil creatures, vampires included, need a reason to kill.

If "they feel like it" counts, sure. But you're arguing against a strawman you created through an over-generalization..

A human could attack anyone on those same criteria. If living in a D&D world, would you also kill all humans on sight?

False equivalency. Undead are not equal to the living. Something Tsukiko didn't get either.