Political Correctness gone Baa-baa

I, like many others last week, was astonished and bewildered to read the story of an overly politically correct nursery.
For those who don't know what I'm referring to, the brief overview is thus: A nursery has recently enforced a rule, claiming that the rhyme 'Baa Baa Black Sheep' should be changed to 'Baa Baa Rainbow Sheep'
Parents were outraged and confused to find out that their children were being taught this but the headteacher defended his decision saying that children have to be taught that minority groups shouldn't be highlighted.
Well, I can't think of more of a minority than a rainbow sheep...
What are parents meant to say to their kids!
Child: (pointing to black sheep) Mummy, mummy, whats that!?
Mother: Oh, that's a rainbow sheep son.

So, judging by this headteachers morals, are we now to refer to balck people as rainbow people? What kind of lesson is this to children.
Bloody mad I tell you!!!