Whilst I think that its all a load of overly PC bullshit over a simple rhyme (although it would never even occur to me to use the word) he really SHOULD have known better in this day and age, particularly considering his previous efforts.
For the record, we said 'Catch a tigger by the toe'.
I doubt a Tigger would have been very happy about it, but I always pictured it being Tigger from Winnie The Poo, and it never once dawned on me that it could be substituted for the 'N' word. That said, we we never once taught it, never heard it, never knew anything much about it, we were never told 'Do not say that word', it was just never discussed. The product of living in an almost exclusively white area I guess.