Margot, why am I guessing you only read one side of the history?
Bill Cameron, does Farley Mowat discuss the possibility that cairns and boat-roofed (or hide-roofed) houses might have been built by the actual Native Americans and Greenlanders? It is good to have a reminder that the Celts were probably not the original inhabitants of Britain and Ireland, though.
Harry O, don't you linguists distinguish between accent and dialect? In "lang may your lum reek" you can certainly argue that the first three words are the same as words in my dialect or yours, but pronounced differently--that difference being indicated for lang/long by a difference in spelling. On the other hand, there's no "lum" in the way I speak, and this meaning of "reek" has been obsolete for centuries in most of the U.S. and England. Surely this is more than a difference in accent?
Whether it amounts to a difference in language is another question, and as you say, some of the people on both sides have political agendas. But that doesn't make the "Scots is a language" side right or wrong. So where can we find the official definition of "language"? (And does this official definition have any political bias?)