The buzzword to be afraid of is establishment, not socialist. Trump will destroy Hillary in the same way he destroyed Jeb. The problem Hillary will have is that she has nothing to counter with. She is the embodiment of everything wrong with politics, much like Jeb. You will see soundbite after soundbite of her lying. All she can do is pray that enough people are afraid of a Trump presidency and she gets the lesser of two evils vote.
Bernie, on the other hand, completely nullifies Trump's anti-establishment message. You can say socialist until you're blue in the face, but then what. Bernie keeps to his message, and people either love him and his message, or just love him. Trump will never lose the crazy vote, but against Bernie, that's all he has. Against Hillary, he gets the angry, and the frustrated vote, and that's a lot of votes.