Politicians lie. Finding an honest politician is like finding a needle in a haystack. Except that needle is disguised as another piece of hay. And you don't know where the haystack is. I've not seen a single political campaign in which both sides didn't attempt to slander the other. Never trust a politician to be totally honest, especially when discussing a political opponent.
That's not to say that I like Clinton. I think she would be a terrible president and is more dishonest than Sanders is. I don't trust politicians to serve the public and be ethical as opposed to being self-serving.
Bernie Sanders seems overall like a good guy and has said that he won't get dirty in the campaign, but he has already started releasing ads that are skirting the truth in regards to Hillary Clinton. He may have good intentions, but ultimately he wants to be president of the United States.
Bernie Sanders is the most informed candidate out there, however, I do not believe anyone should take the word of any politician as the complete truth. The only way to do that is to read a lot and refuse to take anything at face value. Taking the word of only one person, most especially if they are a politician is foolish.
It's difficult to trust any politician, especially when he or she is attacking another candidate. However, a fact-checker for PolitiFact found that Bernie Sanders tells the truth more often than any other candidate in this election. Granted, he only tells the truth 54 percent of the time, according to this fact-checker. However, that's a very high percentage compared to most of the other candidates. For example, Ben Carson and Donald Trump both tell the truth a shocking less than 10 percent of the time.
It is the nature of politics for politicians to present their opponents in a way that makes them look like the worst choice. A politician couldn't possibly present all of the information, pro or con, regarding their opponent. The media will only present what is best for it. Voters need to research claims for themselves.