i take it you wouldn't mind if i came and wiped my penis all over your lunch then? no?
I wouldn't particularly want you to wipe your elbows all over my lunch either, so that's perhaps not the greatest analogy.
Here's a better one, have you had the pleasure of a young lady being goodly enough to put your lunch-desecrating appendage into her mouth? When presented with such an appealing offer, were your first words to her "hold on luv, I'd better just go and give it a scrub first?" Or conversely, would you take a woman to the brink of sexual ecstasy and then go "would you mind just popping off to hose yourself down before I visit down there? Ta."
If you accidentally pee on your hands then they need washing of course. I wouldn't expect you to wash your hands after merely touching your nob unless you've got OCD or hygene issues. If you were preparing food then I'd expect you to wash your hands before doing so irrespective of any prior manipulations you may have been undertaking.