There’s one where Walliams is a racist manager at the airport, he spot checks all brown people coming in and even extends it to his own staff.
There’s a scene where he’s interviewing “Taj” and he’s being racist, asking him where he’s from and Taj (Lucas) says “Bradford”.
It’s taking the piss out of the bigoted views of the manager, not Taj.
Another one is an ex cop who’s turned driving instructor, he goes into cop mode telling his student they’ll do a role play. He then pretends he’s pulled his student over and is grilling him on speeding, at the end he says “now on ya way you ***** bastard”, but the student is white.
Again, it’s taking the piss out of the ex cop, being ingrained in stupid racist views that he can’t shake off.
The one that could be offensive is “ting tong” the mail order bride, but again, I think it’s taking the piss out of the guy ordering the bride. The fact they’ve called the character ting tong could be offensive but it’s a joke at how ridiculous it is.
They’re stereotyping British ignorance in the whole show, that’s the point.