Far from throwing votes away, protest votes are one way that citizens can tell the government that they're unhappy with the election process and their choice of candidates. If there are Sanders supporters who want to protest Clinton's nomination and continued candidacy, they should. Likewise, they should feel free to protest Trump's run for president. Yes, doing so could split the Democratic vote. So what.
If Sanders' supporters want to cast a protest vote, I don't think anyone should stop them. Now that it has come to light that the Democratic primary was a farce, I think Bernie Sanders' supporters have a right to cast a protest vote if they want to. I don't think it will change the outcome of the race either way.
Just for the record, I am not a democrat. I do however know that a protest vote would not work for Sanders. It would work against him. Sanders believes in a more liberal society, something his supporters want too. Now as most of us know, Clinton is more liberal than Trump, so wouldn't Sanders supporters want Clinton as president? Now, why would This guarantee a democrat loss? Well, look at the election of 1912. Theodore Roosevelt formed the Bull Moose Party to purposefully split the vote. He was successful in doing so. Why would this election be any different?
Bernie Sanders' legion of supporters should not cast a protest vote. Although they are disappointed their candidate did not win the nomination, Hillary Clinton is the next best option. Casting a protest vote to third party candidate, or writing in someone, risks tilting the election to Donald Trump, a far worse outcome.
No, Sanders' supporters should not cast a protest vote because Clinton believes most of what Sanders stood for. Trump, on the other hand, is a racist celebrity who should not be able to run for office. Sanders' supporters should fall in line behind Clinton and elevate her to the presidency.