Aim I unreasonable to think that if you haven't needed your autism diagnosis before now, it is irresponsible (and worse, lets down the next generation of autistic children who will continue to think being autistic is something to be ashamed of) to hide behind it when you have screwed up?
I don't agree with this part because there are plenty of people who have lived a life of feeling they don't fit in, committing social faux pas constantly, not really "getting" work colleague/team dynamics, putting their foot in their mouths constantly, had relationships fall apart, failed at school, been unable to maintain friendships and/or friendship groups, struggle to socialise, and suffer greatly because of all that, and it's only when they are diagnosed, come to terms with the diagnosis, understand it, accept it, and can retroactively see why it explains a lot about their lives that they can begin to live in a much happier, more relaxed, and comfortable state.
It isn't about "not needing" your diagnosis. Some people do not or will not accept a diagnosis and live in denial. Some don't get diagnoses until later in life, some never do. Some people are fortunate in that they conform and function well enough that their diagnosis isn't always particularly impairing, so that gives rise to the notion that they have no "need" of it.
I've made this point repeatedly on here because there is a lot of understandable denial, but some autistic people, myself included, have a history of being perceived as behaving like an "arsehole" entirely because of autistic disfunction. Autism absolutely can be the reason for awful behaviour, but some people don't seem to be able to grasp the difference between the concept of an "excuse" and an "explanation". They are not one and the same thing. Autism can be a very present and relevant factor, so no, I don't accept that where and when Autism is pertinent it is always a case of "hiding" behind it when you have "screwed up".
For the avoidance of doubt, I do not believe that in Gregg Wallace's particular case all the things that are emerging are "explained" by Autism. Some of it, possibly. Inappropriate conversation topics that are, in themselves, not necessarily taboo topics but are inappropriate because of unfamiliarity with the recipient, or because they are initiated in an inappropriate setting is very much an autistic trait, but assaulting people, indulging in exhibitionism, and making clearly unwanted sexual remarks is just the sign of a creep.
The thing about a diagnosis is nobody needs one, until they do. When exactly does your autism diagnosis become "needed"? After all, it's a condition we're born with, so surely every autistic person will encounter a point in their lives where their diagnosis becomes "needed" when it previously was not, even if that is as early as the day they are born. There are a fortunate few individuals like those I mentioned earlier who get through life largely unimpaired, but they are still autistic, and strictly speaking, they "need" their diagnosis whether they believe they do or not because it is also a legal state, not just a condition.