I support the right of candidates to run in any election they like. They should not have to drop out just because they are going to lose. The idea that they should is bizarre and no one has ever put it forward except Hillary supports at this current moment.
Honestly, I really don't think very many Hillary supporters would have been desperate for Sanders to drop out if he had stuck to running on the issues. What worries them (and me) is the vitriolic nature of the campaign against Clinton, the conpiracy theory nonsense, the Bernie Or Bust s**t, the talk about a "contested" convention and the growing feeling that Sanders might not wholeheartedly endorse and campaign for Clinton in the end.
Nobody serious (not counting message boards) ever thought that Clinton would not support Obama in 2008 or vice versa. Clinton and Obama are totally committed to the democratic party. Sanders is not.
To be clear, I would still be surprised if Sanders did not endorse Clinton, but I'm sceptical as to how forcefully he will do it. I was never sceptical that Clinton would get fully behind Obama in 2008.