For a vegan is killing an insect unethical?

It's not about whether or not an animal is clified as worthy of saving. Vegans don't inflict unnecessary suffering on any animals, but there are cases where, if vermin are putting their family's health and safety at risk, something has to be done. I probably step on insects every day without knowing it; I'm not a Jain and I don't sweep the ground in front of me. If my house was infested with fleas, I'd exterminate because they'd pose health and safety risks to my family and my dog. I could never justify killing a scallop because scallops will never infest my home, bite my loved ones or spread disease to my family.