I agree, gungnir, that to take one letter from Tolkien and claim that as irrefutable proof would be unwarranted. However, I don't believe I have done that. I merely state there is some evidence. I further qualify this by saying I do not find this evidence definitive.
Having said that, there are situational similarities between the diasporic Jews and the diasporic dwarves, especially pre-Hobbit. The clue is in the adjective, 'diasporic'. Before the destruction of Smaug, the dwarves are spread, far and wide, itinerant, without residence in a spiritual home. It is this aspect, allied with linguistic similarities to semitic language, that point to at least some identification with Jewish influence. For Tolkien, linguistics were of paramount importance, and I find it hard to believe that he would chose a semitic base for the dwarvish language arbitrarily.