I have to say that I initially felt slightly uncomfortable reading the study results published by Jillian Austin and colleagues  providing "preliminary validation for the use of autism disclosure cards in buffering negative judgment." Uncomfortable because, despite the fact that it is human nature for people to stop, stare and perhaps question something when it seems 'out of the ordinary', the idea that when children with autism specifically 'misbehave' in a public place their parents need to somehow justify their child's behaviour to a staring crowd of strangers seems a trifle unfair.
As is the experience of most parents, whether their child is diagnosed or not with autism or anything else, children are not always 'little angels' every time they are out and about ("no, it is not appropriate to start a public conversation about farting when one 'catches a whiff' of something in the shopping centre"). Most parents can usually get away with a nervous smile to any interested on-lookers (or nosey parkers) and that really should be the end of it. Of course, for some children under some circumstances, behaviour can sometimes go beyond just tantrums and onward can raise a few eyebrows but...
Austin et al started with the premise that parents of children with autism are "increasingly using disclosure cards to reduce negative perceptions" when out and about with their children to make "an invisible diagnosis apparent". They devised an experiment using "vignettes of a parent-child interaction in which the child was misbehaving and investigated the efficacy on 160 parents' perceptions." Disclosure cards were provided to some of the parent participants all of whom had at least one child aged between 6-12 years. Various factors covering "Maternal Skill Deficit and Negative Reaction" and "Sympathy for Mother" were analysed as a function of receipt of disclosure cards or not.
"Those who received the disclosure card reported significantly lower Maternal Skill Deficit and Negative Reaction to the Dyad and no difference in Sympathy for the Mother." In other words, making an 'invisible' diagnosis more visible seemed to have an effect in terms of views around 'it must the parent's fault that their child is behaving that way' (negative judgement) but did little when it came to empathising with the mother's position in that situation.
Austin and colleagues discuss how the 'invisibility' of autism and frames of reference - "people will evaluate and compare individuals to some perceived norm or standard" - in this case, so-called typically developing children, may be driving forces underlying those negative judgements from others about children on the spectrum and their parents. I can't quibble with this line of thought or what impact it might have on children and their parents (and other significant others). But it strikes me that in these days of increased numbers of children being diagnosed with autism (see here) - indeed the numbers just keep on growing - and accompanying high-profile campaigns to raise awareness about autism, movement towards the idea that every parent has to 'identify' their child as being on the autism spectrum as and when they, pardon my French, 'fart the wrong way' seems to place too much emphasis on the child and parent and not enough on their fellow citizens and their own understanding and reactions.
OK, I get that people have busy lives and that outside of media depictions (see here), most people wouldn't typically ask 'could it be autism?' when a child has a 'meltdown' in a public spot. I also get that under some circumstances, making particular groups of people aware of a person's autism might be a good thing as per contact with law enforcement agencies for example. The question however of whether strangers really need to be given quite sensitive information about a person and 'their diagnosis' just because they (the stranger) 'can't deal with a particular situation' strikes me as being more than a little one-sided...
 Austin JE. et al. Influencing Perception About Children with Autism and their Parents Using Disclosure Cards. J Autism Dev Disord. 2016 May 30.
Austin JE, Zinke VL, & Davies WH (2016). Influencing Perception About Children with Autism and their Parents Using Disclosure Cards. Journal of autism and developmental disorders PMID: 27241346