Let me tell you a secret. The only component that can make a cat go blind is called Taurine. And yes, if you are giving your cat ANY type of diet that doesn't have Taurine on it, he will go blind, no matter if your diet has got meat on it or not.
The only disease a cat can spread with their feces only affect pregnant woman if she eats the cats feces, so again you are talking a bunch of non-sense.
And no vegans do not practice coprophagy because this would be just stupid as eating meat. Feces and urine are made of everything your body REFUSES to absorb. Everything that is in excess or your digestive system cannot break and absorb.
I don't know what kind of vegan people you met over there, but it is absolutely possible to replace or supplement every single nutrient having a vegan diet. Its all about balance, If you eat only MEAT MEAT MEAT MEAT MEAT MEAT MEAT and nothing else I beat you will get seriously ill. The same applies to someone that does a "vegan diet" in the wrong way.
You need to review your ideas and go study a bit more of biology, nutrition and physiology (animal and human) before you go around on forums spreading words without having any idea of what you are talking about.
YES! PLEASE! Feed your cats a vegan diet!
This way your cats will go irreversibly blind and stay at your own home instead of destroying all wildlife and spreading their diseases through their feces everywhere they go.
(Vegans are so stupid that they don't even realize whey they were born with canine teeth. I wonder if they practice coprophagy, like many herbivores do. Eating their own feces in order to be able to extract enough nutrients out of their nutrient-deficient diet. Perhaps this is why most vagans are as stupid or insane as they are. Not enough nutrition, their minds aren't firing on all cylinders. Saying "EAT SH!T" to a vegan is only wishing them better health you know.)