....Unless you found yourself in a place like Berkley last night. At that point, anything goes. Keep your head on a swivel.
At first I thought it might be someone who supports President Trump.
However, I quickly realized that this couldn't be. A Trump supporter wouldn't refer to another one as a "p**** grabber" or "science hater." For one thing, neither Trump nor his supporters would consider themselves such or would admire anyone who did. To refer to me as an "American" suggests that the writer is not an American and does not consider himself an American. I don't know what the reference to minimum wage means.
And you are absolutely right. It's unlike people like us to stick scary notes on cars and slink away in the dark.