While I am sure that the vandals make up only a small percentage of Trump supporters and, as you have said, some of this happens in every election, but it does seem that the magnitude and intensity of the destruction has been much greater this year.
A lot of that is due to the attitude and style of expression of their candidate. Trump is always angry. He is always feeling wronged and he is always seeking revenge. Part of his campaign strategy is to lie, cheat and demonize the opposition.
But the main message is that Trump, and many of his followers do not care for democracy. They cannot rationally respond to criticism. They saw Trump in the TV debate. He had nothing to offer but bullying and trying to destroy any possibility of a discussion of idea. Which is what these people are doing by tearing down the signs.
Still, they are less dangerous than the gangs with guns who want to kidnap Governors. Those are the die-hard Trump followers, the people he admires.