Why do employers feel they can use my son to tick a box because he's autistic

I'm absolutely hopping mad today.

My son is on the autistic spectrum, he's 21 years old.  He is the smartest, most compassionate, non-judgemental person I know. He works as a special educational needs teaching assistant, he volunteers for a mental health charity, and as a cadet leader.  He has his issues but he's worked so hard to manage them, in fact many people are surprised when they learn he is autistic - most just think he's a bit quirky.

So why am I hopping mad? Well he had an interview today for PCSO. He spent weeks preparing for it, put together a presentation, had to complete online psychometric tests, and then today he was interviewed.........he was interviewed on his disability, not on his ability. He was asked "as a PCSO you can be subject to a lot of name calling. How would you cope with that, being on the autistic spectrum?" "can you tell me a time when you have been criticised? How did you deal with that, being on the autistic spectrum?"  So much for protected characteristic! Imagine asking someone how they would deal with something 'being a woman, being gay, being black'.  They'd be sacked, and rightly so. It was a very negative experience and like they'd already made up their minds, but interviewing him ticked a box.

I shouldn't be surprised though. He went for an interview with a so called charity about a year ago. They were Disability Confident. He attended for an interview taking with him his presentation that he had spent a long time preparing and that was a required part of the interview. When he got there they said "oh, you don't have to bother with the presentation, we'll just do the interview" about 20 minutes later he was done. They had obviously just invited him for interview because they had to under Disability Confident.

Why do employers think that disabled people are just for them to use to tick boxes or get pointless little accolades like 'Disability Confident' that they can plaster all over their corporate material. Who do they think they are to waste my sons time and put him through the stress of interview knowing they have no intention of even considering him for the job?

Does anyone else have experiences like this. My son has always been open about his diagnosis, perhaps naively believing everyone is non judgemental like him.  I'm thinking of advising my son to withhold this information from any future employer.