Sanders knows he needs Clinton voters in 2016 to win the nomination in 2020. He doesn't want to step on too many toes, which is why he hasn't talked at all about Brazile's revelations.
It probably wouldn't matter much since everyone Gillibrand to De Blasio is looking to distance themselves from the toxic Clinton brand. Sanders is already more popular with Clinton voters than Clinton herself.
It probably doesn't make much sense to go back to the 90s & debate if Clinton should resign. You can call his actions deplorable, move on & look to the future. That is what all smart leaders should do. It is enough to boldly condemn his actions for what they were. It is not Monica but Paula Jones & others. Why did Bill pay almost 1M $ to Paula for settlement if he wasn't guilty?
When we are blasting Conyers for settling, what about Bill Clinton ?