Maybe in some circles but I think most people wouldn't care. There's nothing derogatory about 'Black Flash'. Ellery Hanley was called 'The Black Pearl' and he was still playing relatively recently. I'm sure there are other more recent examples.
What I heard back in the late 70s was appalling stuff like, "go back to Wilcannia, ya black ****". And worse. I can't imagine anyone getting away with that at the SCG in 2012. Apart from the fact that Corowa came from Murwillumbah and nowhere near Wilcannia, the taunt was miserable, stupid and not even remotely humorous. But racists are not born with a brain.
I became a part time fan of Larry Corowa for a little while after that (even though he played for Balmain). I distinctly remember Frank Hyde talking up Corowa's try-scoring abilities and naming him in his preferred Kangaroo side because, according to Frank, "you just can't ignore him..."