Yesmadam, it first came to my notice in the 80s when, basically, excluded groups (gay/disabled/ethnic minorities etc) started to appear to becoming more aware and demanding of their rights. As a parallel to this, there were some excellent left-wing initiatives taking place in the Metropolitan Borough Councils (so Thatcher abolished them, apart from the GLC, of which Ken Livingstone was leader). Then, whenever something smacked too much of left wing ideas, particularly if it had a silly name, it was riduculed. A case in point was the supposed banning of the term 'blackboard' in case it offended black people. Of course this would have been a ridiculous claim, had it been true, but it wasn't. It was made up and stirred up by the likes of the Sun/Dail Mail to get apolitical or right wing hackles up. It then led to people's claims that such a thing was racist, homophobic etc to become easily dismissed by the blanket term 'Politically Correct', making it safe again for bigots to use offensive and abusive language/bahaviour. People who are actually trying to promote equality in society can now be easily laughed at and said to be 'too PC'.
It has also occurred alongside the (Thatcher-led but continued by Blair) depoliticising of education and society, leading to a situation where few people are capable of presenting a real political argument.
'Till Death Us Do Part' was set in a totally different era, but even then, the joke was supposed to be on Alf Garnett - people were supposed to be laughing at him, but too many agreed with him and laughed with him. i was only a kid and loved the programme but even then found the real star of the show to be Dandy Nichols, who took the p$ss out of him mercilessly.