There was no need for Hillary to throw Bernie Sanders under the bus like she did during the debate, but I also don't think that Trump had any right to even make a comment towards the situation. Hopefully people will see that both Trump and Hillary are horrible presidential choices.
Clinton is currently competing with Sanders. Why would throwing him under the bus be disloyal? She is trying to separate herself from him. I think Trump saw this as an opportunity to try to further divide the Democrats. I would expect Clinton to continue to criticize Sanders as long as they are both in the race.
Donald Trump is offering an opinion from the outside about the inner politics in the DNC. I do not hold that he has any unique perspective on their combative roles. How Hilary Clinton is being disloyal is another perplexing statement because is she using the DNC's favoritism in her favor or is she purposefully hurting Bernie Sanders' chances? Is she being disloyal or disrespectful to the part or to the person?
No, Clinton is not disloyal for "throwing Sanders under the bus" as Trump stated. Clinton and Sanders are competing with each other to be President of the United States of America. This is a big deal and of coarse candidates are going to take shots at each other. They are not supposed to hold hands and sing Kumbyah.