I don't expect others to feel the same. I have chosen to give value to one over the other simply because I would prefer a world where we collaborate towards collective happiness, joy, and pleasure. I suspect many others believe that working towards the prosperity of the collective will hamper their ability to find personal prosperity, and I simply think they are wrong. I think such a case boils down to chasing momentary pleasure over long-lasting pleasure, because that is my experience with such people.
In a way I believe in tangible karma; those who work to bring pleasure to those around them are occasionally taken advantage of, but more often are given pleasure in turn. Likewise, I've never met a self-centered asshole who isn't consistantly overcome with unhappiness, while almost universally blaming that unhappiness on external factors.
I plant trees I will never get to sit under because I appreciate those before me who did the same. Again, that is no more than what I have chosen to give value to.
But this is a bit of a digression. The reality is these are the wisdoms of my experiences, and I wager there's no universal truths in them. Nothing matters, so I look to these experiences and see that a co-operative, collaborative life looks more pleasurable. So I strive towards one, encourage others to do the same, and refuse to tolerate those that would actively work to steal happiness from others. Yes, I am aware that the inverse is equally true - why is it wrong to steal happiness from others if nothing matters - but this perspective is simply not the one I have chosen to place value on. Arbitrary? Sure. It still represents the best way I've found to enjoy life.
There's one massive quality that makes positive Nihilism different from Absurdism. Absurdism states that trying to create meaning in a chaotic universe puts you at odds with it. Therefore, doing so creates unhappiness. Optimistic Nihilism, as the common thought I was trying to convey but incorrectly labelled is called, believes that without inherent meaning in our chaotic universe, we are free to create whatever meaning we desire.
Both believe the universe is inherently chaotic and meaingless. Only one believes that you can successfully create meaning.