Diamondback rattlesnakes are what they are, and do not pretend to be elder statesmen. That said, elder statesmen are supposed to be responding to some kind of moral compass and employing some kind of rationality in their pronouncements.
Harry Reid lacks both a moral compass and any kind of rational thinking.
Also the snakes don’t usually go looking for trouble.
Diamondbacks eat vermin. That’s quite a few steps up in terms of usefulness contrasted with Mr. Reid. Diamondbacks are also polite enough to let you know if you’re getting too close to them.