For the record, science disagrees with you. According to an analysis of all current research, there is no statistically significant difference of cat heath when fed a nutritionally sufficient vegan diet. Of there is a similarly high quality study that finds that a nutritionally sufficient vegan diet is worse for cats I would love to see it.

The vegan diet we are talking about isn't a bunch of vegetables, it's a manufactured dry food specifically designed to have all the nutrients a cat needs.

People often use the obligate carnivore excuse, but use it in an unscientific way. Obligate carnivores have nutritional needs that can only be meet through meat in the wild, but humans are perfectly capable of manufacturing these nutrients. We are so good at it that we supplement these synthetic nutrients in meat based cat food already.

This is a contentious issue for most people, and it can be hard when you are very passionate about something to look at the evidence and change your opinion. I've looked at a decent number of studies on the topic recently, and they all seen to point to the conclusion that a diet without meat can be healthy for cats, so long as it contains all the nutrients they need.