We've been doing it for about 10,000 years.
Let's take it as a given that Monsanto are evil bastards who do not have your best interests at heart -- they are a corporation after all, so that's a tautology.
However, people who are against genetic modification of our food sources are basically using the same arguments as the anti-vaxxers. It's anti-science magical thinking.
If you're wealthy enough that you can afford the artisanal, bespoke grapes with the seeds and bugs left in, enjoy them.
but if you want all our food to be constructed using pre-Paleolithic methods, get ready for a die-off on the order of 6.5 billion people, because without the optimization of agriculture, that's around the planet's carrying capacity.
Prop 37 was stupid. It was full of loopholes and solved no real-world problems. It might as well have said, "this is a non-binding resolution that Monsanto Bad!" Which they are. But that's not the point.