If the only thing Bernie (who is a horrible prick of a politician but less so than the rest) does is convince America that their version of 'commie' is what the like of Europe consider to be normal then he has done his job. America needs a president who, without necessarily achieving anything, can normalise ideas like free healthcare and health so that eventually America can actually have a 'left wing' party. Although it is cute to see posters label someone 'leftist' when they'd be centre right in Europe. If you think Sanders is a commie then you better never leave America or you're head will explode.
Anyway Sanders is a terrible candidate (welcome to politics where everyone of them are shit) but this time you actually have a 'lesser evil' to choose, as opposed to rape apologist 'feminist' champion Clinton.
If the only thing that a moderate like Bernie achieves is to teach America about true progressiveness then he will have done his job. Then hopefully you'll be ready to elect a proper 'left' candidate and not some old rich guy masquerading as one.
Elect one of the others and it suggests you haven't learnt anything since Trump and that you are happy with the America you have now.
Edit: free healthcare and education it meant to say.