Hi ,as my original post was made assuming U.S drone laws were similar to those in the EU which require 30m separation from any object not under your control , ie ships , trains , earth moving equipment etc , so as I stated previously ,I was wrong in stating that he broke any rules .I'm not aware that there is an FAA rule on drone-train separation. There are newly updated rules on flying over people and cars, and he seems to be in compliance with them. Alternatively, there is no evidence on this video that he is NOT in compliance.
As far as the message goes, we're allowed to do that in America.