"Why do cat owners think that they have the right to allow their animals to roam freely, and crap in my flowerbed?"--
"Because they're cats. Birds are probably pooping in your yard too. Unless some real injury or property damage occurs, it's no big deal."
Then you shouldn't complain if I come over and crap in your flower bed and pee off your deck.
Hey, you can come pee in my yard if you want to! It keeps the squirrels away! ;)