Peter: The reason why it's difficult to take deal with issues raised in the letter is that the writer is largely dealing in hyperbole and bromides.  

Here's an example: "Trump’s tax cuts would increase investment, boost productivity and wages and increase innovation and opportunities for all Americans." That's silly. Tax cuts for the super-wealthy don't result in any of those things (or if they do the effect is neglible). The Bush tax cuts sure didn't result in that stuff. 

Most of the other statement are similar. Just a whole bucket of simplistic statements with little regard for the complexity of any of these issues.