I thought I read that Luigi actually claimed the manifest as his own, but searching around does not bear that out.
Best I can tell, neither the police nor the major media outlets released it in full after the arrest or shortly thereafter, but it was found and shared by this guy later: https://www.kenklippenstein.com/p/luigis-manifesto
Long story short, I still have no clue about the authenticity. One recent headline says Luigi's legal team doesn't want it admissible as evidence for the trial, for what that's worth.
My comment was more about the hypocrisy of the term "American values". The people who most loudly espouse "American Values" rarely do more than pay lip service to ideals they think are good in a vacuum, but never actually support in practice when those values are tested even a little bit (democracy, equality, free speech, the right to protest, etc etc).
That may not be a uniquely American trait, either, but it is still annoyingly present enough it warrants complaining about.