Having just read through all your threads, I think autism is a factor in the problems you're experiencing, yes. In particular, the flak you are getting on Mumsnet is mostly due to some of your brief and blunt replies to comments from others - and your creation of multiple threads on the same topic, which is breaking an unwritten rule of how people "should" communicate on here.
I don't personally read your comments as being as "rude" as a lot of posters do, because I have close friends who are autistic and are similarly brief and blunt without meaning to be rude! (I also have friends who are autistic who do not do this, just to be clear). So the fact that you provided the context of being autistic was enough for me to make the assumption that this is the reason you write like that. Unfortunately the advice given is correct in that you will continue to receive negative reactions from the majority of people when you respond in this way. It's annoying for you, because (I think) you are just trying to reply quickly and accurately and not waste time, but it's how most people expect communication to be - more blather added in to "be polite".
Hope that makes sense! (This short sentence is an example of blather, used to soften my comments above and try to instil a sense of "I'm trying to help" context to my words. This is important when typing because people can't hear my friendly tone of voice or see my facial expressions. It can also be important in person if, again due to autism, your facial expressions and tone of voice don't automatically match your intentions/how people expect you to look/sound in this context.)
Autism often includes difficulty with communication/social skills, and you have to try to learn the skills manually that most neurotypical folk can do automatically. This is especially important in a work context (or online forum) where people don't know you so won't assume the best. You've been offered a fair bit of advice on how to do this in your previous threads, such as adding certain lines or comments to demonstrate your intention to be polite, so I won't try to repeat that here.
Just to add - I'm not perfect at this either - so if anyone has read any of the above and objects to it, apologies in advance! Just trying to help OP out with my perspective.