Work disciplinary

I'm new here,but after some advice.my son has asperger and has just had a disciplinary at work in relation to social media comments.He has worked for the company for 7 years,has an exemplary record,and it is his first offence.He is very good at hiding his asperger s but has always been honest, most staff know he's on the spectrum.The whole disciplinary process has heightened his anxiety which he has tried to explain,he received the letter for investigating 30 minutes before meeting,with limited information of what he had been accused of,which made him panic,questions sent him into sensory overload,room became smaller and he felt alone.It is difficult for him o relate social media policy to his actions, can be impulsive,doesn't always realise consequences of actions.He only name company once,other flagged comments are general observations,he used hashtag work,but did not put my work, so in his mind could relate to any work,and nowhere does it mention where he works.During the disciplinary the manager chairing the meeting said I quote" so you want preferential treatment because you are aspergic",to which he replied no,in 7 years I've never asked for preferential treatment, and I'm not asking now.He is to be issued  with a written warning,that will remain on his file for year.Any advice much appreciated.