Disabilist jokes on Radio 4's Everyone Quite Likes Justin

I usually listen to the comedy half-hour on Radio 4 between 6:30 and 7.

On Wednesday, I tuned in halfway through a new show called Everyone Quite Likes Justin.

After a few minutes, one of the characters said. "I've seen how you go when you're around Lisa. In that soft voice."

"What soft voice?"

"That. Don't be like that around her. People will think she's your carer."

This comment implies that disabled people who require carers talk in "a soft voice...a silly, needy voice*", and that the way they talk is something to laugh at.

The phrase "People will think she's your carer" is also commonly used as an insult, implying that disabled people are stupid.

Also the sitcom used "mental" as slang for "shocking". "Rocked it out...mental...mental"

Why is this hateful show on Radio 4?

*Used later in the show in relation to the voice.