Alright, so here's what happened.
Bernie did say that he thought that a woman couldn't win (against Trump), but in the usual context of "the people aren't ready, are too bigoted, Trump will lob sexist attacks, etc.".
Warren, being the evil c*nt that she is, had this leak. It plants the seeds of doubt in people's mind that Bernie is anti-woman after all.
Bernie, to his credit, could've explained the context of what he was saying, but smartly denied ever saying it at all because it's unnecessary and would only hurt him. Some people wouldn't believe him, so admitting that it happened, regardless of context, would be the wrong move. This is why Bernie denied ever saying it at all, because you cannot prove otherwise, it's a private conversation. Basically, all is fair in love and war, and it's a moot point to imply Sanders is sexist given his progressive past. Sanders was like, "Fine *****, you want to play dirty, I'll play dirty too".
This is why Warren is whining about "You called me a liar on national TV". She can say that in good faith, because she's technically not lying, but she knows the implication could only hurt Bernie, and so she's being a slime ball. Sanders responded by denying it ever happened, because he knows she knows the context and is only doing this for political gain. The only thing that could **** this up for him now is if he tries to be the giant cuck that he actually is and explain what really happened.
Sanders did the right thing by denying he ever said it in the first place, and he needs to shut the **** up. If this goes on, he should remind her that she's not a native American.