And what is supposed to be the problem exactly?
At least the message is clear and straight forward. But yeah, it sure is a big change from all the usual conventional and formal messages that favor the form over the content.
I have read, and still am reading, official communicates, documents and other letters sent and shared by various administrations, and though the form of Trump's letter is unusual, going all mad and ad hominem about it is... questionable. Sure, there are people who don't like Trump for valid reasons, other don't like him "just because", but it is not as if anybody were asking your advice on how things are conducted either.
If it upsets you that much though, you can still send the WH your resume. Maybe you'll get a job a speech-writer, State Secretary for "whatever", communication expert, etc... Who knows, if Trump's team is that incompetent, you'll obviously end up shining.