Your arguments are ridiculous - the term 'coloured' is connected with the apartheid. So, fairly logical then that it would be viewed as offensive now and always should have been.
If you are going to call my arguments ridiculous, it would help if you knew what you were talking about.
The Coloureds of SA still call themselves coloured and are not by and large offended by the term, in fact identify themselves by it.
Coloured being offensive in the UK actually comes from the US deep south, where segregation was practiced between "whites" and "coloureds", and the 1960's Black Civil Rights movement preferred the term "black".
The UK eventually picked up "coloured" as offensive due to this (later than 30 years ago, but that is Not To Be Admitted - and explains Sarah's confusion) and used the new US term, "black"
In the US of course, "black" has now been largely replaced with "African-American"
So it is predictably only a matter of time before attempts to see "black" as offensive in the UK will start, and replaced (by "British African"?), as our hand-wringing academics take their cues largely from the US (while professing disdain at all things American, of course).