But the dark side's cookies are poisoned!

Hate can be a good motivator to activate our fight or flight responses but that's only if there is a tangible enemy (like hostile interstellar extraterrestrials, but that's unlikely) to strike at. But all the enemies we have now can only be defeated by love and hope, not fear. Hope is also ultimately the greatest motivator of all. Fear and hate may bring certain people together but it also rips people apart and unjustly singles out certain groups of people for trivial reasons (e.g. the Holocaust). Fear is negative; it breeds resentment and ultimately chips off at your lifespan. Hope can bring people together regardless of age, ethnicity, or gender, all without the seething bloodshed and reduction of lifespan associated with hate and violence. And optimism makes breeding hope easier.