Whut iz u, the gramer pulice?
It’s not grammar, it is the use of the word “gotten” that shows that the writer is deficient in the use of the language. If one were to use “gotten” in a high school or college term paper, their grade would be marked down a few points, if not failed.
In addition, the writer claims that Manson is a mass-murderer and even thT is incorrect in every sense of the term.