This type of emotionalizing really shows a weakness of using morals to control a society - while following the moral makes you feel superior, it in of itself does nothing very useful to control people who don't follow them.
It might inspire a couple people to unthinkingly scapegoat others that "look like" they're transgressing the moral, but in the end people will just hide the bad act, or hide their responsibility to it and nothing will really change.
I don't really agree with the original poster's sentiments, but carnivores tend to produce terrible fertilizer that isn't likely to benefit any city lawns.
Your comment sent me down a Google search asking the question, "Is cat poop good fertilizer?" Most advice seemed to agree with you, but I found a few interesting (if tangential to your point) stories.
The most interesting was this guy in China who made a custom composting system to process cat poop into fertilizer in order to fund his cat sanctuary.
