Context isn't everything, but it is important.
When Till Death Do Us Part was on TV originally it was surrounded by casual racist depictions and normalised bigotry passing as humour. Bernard Manning was on prime time, the Black And White Minstrels had a mid evening slot, a lot of TV drama had black and asian characters as caricatures (often criminal or defined by curry), and Enoch Powell (and sadly, the London dockers) has just done their bit for race relations. Alf Garnett in that context was cutting edge anti-racist satire. He even did a very good job of making a hero out of the 'Scouse git'.