Well if people want to bring up specific instances of is written instead of more of a moral discussion and even the possibility that most of what the world the player is active in could potentially be smear by surface dwellers as someone took some artistic liberty with in the monster orphanage thread. We must first look at what defines "good" in Pathfinder. In the Core Rulebook under Alignment, under Good Vs Evil page 166 it says
"Good implies altruism, respect for life, and a concern
for the dignity of sentient beings. Good characters make
personal sacrifices to help others."
Given this definition it does not call out potentially evil sentient beings as being exempt from being respected has living beings. In fact it sounds like the description of evil to me stated in the next paragraph.
"Evil implies hurting, oppressing, and killing others.
Some evil creatures simply have no compassion for others
and kill without qualms if doing so is convenient. Others
actively pursue evil, killing for sport or out of duty to some
evil deity or master.
"Huh, hurting, oppressing, and killing others really is all happening with declaring an entire species kill on sight. It even calls out killing as a part of duty. I mean people in history have more enough done the same thing, but since this is a fantasy world and real world morality doesn't have any relation to fiction that is off limits.
Now it is stated by the op that drow are "monstrous humanoids" and thus morality does not affect alignment if killed. This is False in two ways; one respect for life does not differentiate between "monstrous humanoids and "normal humanoids", two According to the Advance Race Guide page 103 drow are humanoids with the elf subtype. Therefor killing a drow would be mechanical killing an elf. Furthermore no where does it state that drow are evil in the ARG in fact it explicitly states "...they are not born evil..."(pg. 102). Now this is used to qualify that though they are not evil, there society is. But people can attempt to flee corrupt societies or even given the opportunity to be raised away from said society could be different. (There are people who try to escape shitty societies but hey we can't equate real life to a fantasy world.)
Also if you look at it purely from a political stand point this is a declaration of war. If I was a kingdom I would not want to go to war with a foe who's settlements I don't even know the location of nor is my army equipped to go to war with. But that really doesn't have anything to do with bieng good so I digress.
tldr; Killing an unarmed drow on sight is no different from killing a human on sight, thus it is an evil act, even in the name of someone else.
