I don’t see any evidence this guy did it himself. Just because some people have doesn’t mean he did.
There was a muslim woman in our town that came out to her car with a yellow post-it note on it. It had printed in big block letters like a 3rd grader would scrawl and said something like “mUSLim GO FrOm AmEriKA”
And it was also written in flowing Arabic with proper diction and structure. The last I heard was that the police were “investigating” it. Pretty obvious - and I imagine to be PC they didn’t do anything to her.
Sherlock Holmes would deduce something from the curious incident of the dog in the night. That doesn't mean this guy did it himself, but the entire vandalism incident is unusual in its stealth combined with thoroughness.