The fact he actually appears to have boarded an Amtrak train seems to suggest he knows more about Amtrak than a substantial number of Americans (who either don't know Amtrak exists, doesn't know how to use Amtrak, or simply ignores Amtrak).
Why is it that in order to have a voice in Amtrak, one must have ridden X number of miles on a train, or so many routes? He rode a train, had a very horrible experience that was well below his expectations set for the experience, and decided that something needed to be said about it? Do you honestly think that by writing Amtrak about this experience will make any difference? Further - does writing to Union Pacific make any difference?
While it is a stretch to say that the Coast Starlight is proof that the entire Amtrak system is flawed (well, that must be why Delta Airlines is bankrupt, because of that flight they used to run from Portland, OR to Narita, Japan!) - I would likewise say it is a stretch that many people in this country do not travel so frequently or to so many locations, that they require use of more than one Amtrak train or route. Therefore, the Coast Starlight might be the only logical Amtrak route for the majority of his long distance travel needs. He may never have a need to travel to Malta, Montana, or Lamy, New Mexico, or even Portland, Maine. Thus, his response has some merit.
Mr. Perkowski said it right - when something is good, a customer might tell one or two people; when it goes wrong, all hell breaks loose.