The right to free speech in politics trumps local zoning in this case.
Here in NJ, political signs are allowed in my town in the run-up to the elections. For a few weeks every year you can tolerate a few signs. (There may be a modest size limit.)
A yard sign is less intrusive on the neighbors than sending junk mail, going door-to-door, or even just talking.
If you go to a rally, that is fun, but does not reach the uncommited, because the rally will be covered (chances are) by a biassed press. Most of us are not George Soros, and cannot pay for influence the way he does. We have only our vehicles, and our own property.
Such vandalism reeks of intimidation.
Hope there is a follow up and these guys are caught and punished.
(Hey, it could happen.)