Well, if you thought 'Love Thy Neighbour' was non-PC those wonderful chaps at NetworkDVD who specialise in obscure and cult ITC productions, released 'Curry And Chips' last year:
http://www.networkdvd.net/product_info.php?products_id=1131
I've not seen it, but the reputation of this Eric Sykes and Spike Milligan effort is quite notorious.
Probably the worst taste 'sit-com' ever produced was 'Heil Honey I'm Home'. a British show from 1990 that involved the 'amusing' shenanigans of Hitler and Eva Braun living in a flat next to a Jewish couple. It was never aired, can't think why. If really curious to see it, it's on YouTube.
Personally I'd love to see repeats of 'It Ain't Half Hot Mum'.