My neighbor has Bernie sign in yard, what should I do ? ?

Leave them alone. They're allowed to have opinions that differ from your own.

nothing, unless you dont mind having an angry neighbor around

Nothing. You might calmly ask him why he's voting for him, then calmly explain the problem with that. But other than that, do nothing.

set yourself on fire in protest in the middle of the street

Get a job and maybe try to get a life too.

Mind your own business and vote for whomever you want.

Respect his right to an opinion. This is America.

Put up a sign of the candidate you like that's bigger.

Tell him to back Buttigieg because Bernie's now a lost cause.

Congratulate him on having good taste.

try not to laugh so hard at them