"I was slated some time ago as a "racist" for calling Scotch people Scotch!"

It would be way over the top to condemn someone as a racist just because they used the word Scotch especially if they didn't know the fact that the word is out of favour amongst Scots and has been for some time. Originally it was an English contraction for Scottish which became widely used in Scotland itself and of course there was nothing derogatory about it at all. It seems to have gone out of common use in Scotand itself (apart from its use as an adjective with whisky etc) during the 20thC when Scots and Scottish came back into normal usage. Because people know many Scots tend to not like being labled Scotch the word is often used now in a derogatory sense though even at that it is only mildly derogatory. Basically the use and perception of words change. Many Scottish people will be slightly irritated if you call them Scotch but would maybe be a wee bit more resentful if you call them Scotch once you know that they don't like it.