You mean Fruitarians? They certainly exist. I do enjoy how you seem to think that it's inconceivable. HN Favourite Steve Jobs was once a Fruitarian.

https://en.wikipedia.org/wiki/Fruitarianism

I just don't understand how you can have a moral outrage to killing one thing but not another. People seem to do a little dance about plants being not as alive as animals to justify it, but it doesn't make sense to me.