If a person threw chicken crap at the restaurant, the individual should be condemned, arrested, and prosecuted, regardless of his/her political leanings. It is an act of vandalism.
Chicken crap washes off. It is not damage to, or destruction of, property, therefore it is not vandalism. It's maybe, at best, a health code violation, but even that's a stretch since it hit the sidewalk, and pigeons probably crap on that sidewalk all the time.