He used the word "mongoloid" and in his apology, claimed he did not realise its associations.
I have at least one student per term use the word "mong" as an insult and I educate them as to why it is offensive. Same if I hear them use retard - I explain retarder/en retard in French means delayed and they are actually calling someone slow. They also now know how Scope rebranded because the word spastic was used as a slur.
Many kids are open to etymology and are 
when they realise what they have said. They hear the words in the playground and repeat them. They don't always realise they are offending those with or those who know children with Down's syndrome or cerebral palsy until it is pointed out to them.
Many do not use such slurs again, once they know it is derogatory.
Downy is a new slur recently - this is not being used by students defining themselves like Aspie occasionally is, it is being used by others about others. Education is key.
Jamie may not have realised - now he does.
He will now be used by educators as an example of someone who was ignorant (same as Beyonce/Lizzie for using the term "spazz out") so that young people might act as upstanders in the future rather than bystanders as more call out such language.
I heard "gay" used pejoratively last week (was intense in Ali G period, had hoped it had died out by now) - told them one of my kids was gay and I didn't appreciate it being used as an adjective for saying something was lame. They apologised. End.
Cancel culture is deemed by some to be too reactive, we're easily offended etc but if you are in the public eye, you are a role model. Do better.
Jamie would have known he was saying something insulting, put it that way.
The timing of all this is suss though. Looking back at the new, shiny, "we're all safer now" Strictly vibe of that last series - and at least two cast members' "bantz" was offensive to those who heard it [roll eyes emoji - banter is a shite term, reeking of Boys will be boys excuses].
They kept all under wraps during the duration, despite the furore about Wynn's hand on Katya.
Then after the show, the furore over Wynn saying "spitroast" to Jamie when Janette was between them at a photoshoot, and now this story.
producers must have their head in their hands each year.