Bats, squirrels, raccoons and mice are commonly regarded as pests, as they are the animals that people living in urban areas are most likely to come in contact with. The most common response to finding one of these critters in a living space is to call an exterminator, set up traps or bait them with poison.
It's understandable that people may not want wild animals in their house, but it completely overlooks the fact that these animals don't have anywhere else to be. These animals would prefer to live in wooded areas, but the pervasive habitat destruction that took place to make our cities makes it impossible. However, there are steps that urbanites can take that allow these animals to coexist safely and peacefully.