Well, for instance broccoli is KNOWN to be engineered by man. That doesn't mean I don't like it, I do. I just think the benefits of fruit are better, being less tampered with.
Grass grows out of the ground, by itself, not by Monsanto. To me that is a testiment to it's naturalness. I'm sure you would have to take it on a case by case basis.
I'm really not arguing the semantics of what is or is not a vegetable. I'm saying look at how it's grown.