[ not downvoting - it's already low enough.  I do pretty strongly disagree with the thesis, and also find it unclearly written. ]

Did you actually look into Bostrom's writing or his retraction/apology?  It reduces my credibility in your post to see you write "he holds some unpleasant views" rather than "he wrote some provocative messages, which he clearly regrets."  Alternately, pointers to his more scholarly work and a clearer description of which views you find unpleasant and why would go a long way.  Also, perhaps use stronger words than "unpleasant", if you're justifying a wholesale change in approach.

And to the meat of your post, 

the longtermism of Bostrom is a deeply individualistic longtermism and that what we need is a collectivist longtermism. 

Wut.  That's a HUGE jump, even if you'd shown what part of Bostrom's writings were problematic in a coherent way.  I will admit that I start out suspicious (not to say dismissive) of "collective" ideas that are not a strict sum of individuals.  But even for those who believe that somehow the sum is different than the parts, or who focus on different parts of a distribution than I do, it requires a bit of effort to make the logical tie here.

Either we all go into the future together or we don’t go at all. 

Well, no.  The vast majority of us will die, and the future mostly comprises individuals who don't yet exist.   Also, is this intended to be a threat?  Or just a slogan, and I've made an error in trying to make sense of it.

Agnostic on the argument itself, but I really feel LessWrong would be improved if down-voting required a justifying comment.