Broccoli contains cyanide too. The rice arsenic thing is a bigger deal though. Some enterprising entrepreneur needs to come out with a percolating rice maker.
I seem to remember a Bruce Sterling book(Islands in the Net?) where one of the characters avoided vegetables for this reason.
Of cause they try to. It is normal evolutionary behavior of plants. And co-evolution of humans to being able to tolerate this toxins.
In fact, milk and wheat may have compounds, that are addictive.