The media has been declaring Clinton to be the Democratic nominee since the beginning of the election, so of course they want their predictions to come true. Therefore, they seem to have been fairly dismissive of Bernie Sanders throughout his whole campaign. I don't think it's a case of the media "being on Hillary's side" or consciously trying to help her get the nomination, but there definitely has been some bias there.
Hillary Clinton may very well become the Democratic Party's nominee for president in 2016, but she has faced a very strong challenge from Bernie Sanders. In addition to Clinton's challenger for the nomination, she still faces a cloud of suspicion over her email controversy. In short, due to Clinton's primary campaign struggles and her FBI investigation, it was too soon to call her the presumptive nominee.
Hillary Clinton has received more votes and has won more pledged delegates than any other candidate for the Democratic Party's nomination. Senator Sanders has done better than expected in the primary, but the fact of the matter remains that he trails Clinton in the popular vote and pledged delegate count. When the unpledged, or super, delegates are considered, Ms. Clinton's lead becomes insurmountable by Sen. Sanders.
If the numbers are correct and it looks like Hillary Clinton is going to be the nominee than it was not too soon. You can not go by polls but if the primaries are in then there is no question. All it takes is knowing the facts and then there is no question.