You raise an interesting point, unfortunately, it isn't true. Senator Clinton has not won the popular vote so far, that honor goes to Obama. For you to get up and argue that only Hillary has a hope in the November election is stupid. If she is the best candidate, why can't she garner a majority even in her own party?
Hillary is universally despised among the republicans. She is considered a shrew, a bitch, and just about every other insult you can throw at a woman. Further, she has shown herself to fit quite ably into many of the labels: manipulative, calculating bitch is my own personal favorite. Merely assuming that Hillary will win because she is "tough" forgets that she is also considered a bully. There is nothing that people hate worse than a bully. Should HIllary win the nomination, especially now, she will lose. Further, she will lose big.
The republicans were smart, they have a candidate who (nominally) appeals to moderate democrats. If Hillary steals the nomination, I think that the democrats who opt to vote republican will vastly outnumber the republicans who are going to opt to vote democrat. This absolutely nothing to do with sexism and everything to do that the Clintons are manipulative, power hungry and destructive.