Lately when my kids complain about an animal or bug we have tried to explain that even though they can be bothersome they are essential to life as we know it. This has helped them realize that everything has a purpose and reason for living no matter how bothersome.
The other day I was driving in the car with the kids. Driving past a bunch of cows the air filled with the lovely stench of cow poop. The kids always notice this smell and point it out. Of course they started to complain about it again today. Ethan said that he hated cows because they stink so bad. My rebuttal was "but they tasted so good, and milk tastes so good. Without cows we wouldn't have those good tasting foods." I then explained how even though cows poop stinks it also helps plants grow. His response was "then why don't we poop outside?!" All I could do was laugh.