the accuracy of the revival & so forth is largely irrelevant to the discussion

I like the gracious way you concede the point, GUEST.

whether it is (or ever was) intended as racist

Minstrel songs: documented. Use of banjoes and bones (alongside minstrel songs): documented. References to dancing out as "niggering": documented. I think the "ever was" part of the argument is pretty well proved.

As for whether it "is" intended as racist, sometimes it may be, but nobody's suggesting that all blacked-up dancers are racist. Intention isn't the point.

whether it causes significant offence, and I have yet to see evidence of either of these things.

You've been offered two separate quotes from individuals who found it offensive and dismissed them both. How many more shall we collect before you agree that it's 'significant'?