The problem with treating all animals with equal compassion is that some animals are very small and get themselves killed by living amongst us. Like you, I don't deliberately kill most insects and spiders (I do kill grain moths and mosquitoes) but I sometimes kill other little creatures by working: digging a hole kills worms, moving logs kills slugs and centipedes, walking on a sidewalk kills ants. I try to minimize my impact, but at some point you have to draw a line and get on with life.