I love how fawlty towers is the bar you are going by, that's the definition for a slippery slope. You do realise that these racist tears have been shed in the past, when slavery was abolished, when apartheid was abolished, when black people were allowed to vote, when they took off programmes such as love thy neighbour and alf garnett, when people found jim Davidson and Bernard manning odious and offensive.
Look face it, your way of thinking is dying out. We will look back and be aghast that we allowed blackface on tv. There's nothing you can do to stop that.