Why is that the BBC try and alter History?

Why is that the BBC try and alter History?

In a recent Doctor Who, which I have watched since its start, there was an episode about the Doctor going to the times of Oliver Cromwell. In one piece a man was to be hanged and the villages were baying for his blood. In amongst this crowd of Villagers were Black people since when were Black people part of village community in the 1600’s? Another instance was when they had a programme called “Merlin” this was in the time of King Arthur and in this programme they had Black Knights one wonders how many Black people lived in England in the 6^th Century? Then we have the 2012 Olympic Opening Ceremony which featured Black Mill owners in the eighteen hundreds can anyone name one Black Mill owner in that time?

Although the three examples I have given are fictional and therefore the authors are allowed poetic license BUT why change some of the basic facts of History just for Political Correctness? Of course the lefties will call me racist because I bring the subject up but small anomalies in the truth can lead to larger problems. For example Militant Moslems want to ban the history of the Holocaust

PC has to be watched because they want to completely change our History already some are asking for children not to be taught about our British Empire an Empire which made our Country great and gave a great deal to the World admittedly not all good.