The underlying point is not to march alongside someone who disagrees with you, its that there are Boomers and Gen Xrs who agree with you and they've been waiting for enough young people to join them. It's not just Bernie Sanders and no other Boomers. The same Gen X people who grew up on Public Enemy and Rage Against the Machine and still fight for the beliefs espoused in that music are here. We are frustrated that so many young people just seem to want to check out, when we've needed them to help us win these battles for so many years.
When I first became an atheist, only 9% of the US was 'none', meaning atheist, agnostic, or no religion. Now it's 30%. I haven't gone anywhere, just happily watching the world change and I know a lot of it is those younger than I am.