Beyond the bird or wildlife problem, outdoor free roaming cats are just generally a problem. I have two cats and an outdoor cat likes to come and taunt them at the window: it seriously stresses them out. It'll go so far as climbing up screens and damaging them. Cats will also often mark people's houses.

I walk my cats on leashes. I don't understand why cat owners can't understand that people don't want their cat around unmanaged.