Do you actually think Israeli farmers are somehow more despicable than Palestinian farmers? There is an obvious political/ethical choice to do with which government you support but do you really think the farmers get a whole lot of choice over who governs the land they till? How exactly is a farmer an active part of one or other state?
All you're doing is making one innocent person who is unlucky enough to have been born in a bad situation slightly poorer than another innocent person who is unlucky enough to be born in the other bit of a bad situation. entirely apart from the fact that Israeli farms may still employ palestinian workers or vice versa. Either way you're punishing an innocent person for a situation that is not within their control.
I hope you enjoy your completely illusory sense of moral superiority.
Jon