I clearly say that people who behave in ways that we would not expect get described in those terms. Some people who behave in ways we do not expect are autistic.
Yes, and some people who are autistic behave in ways that we do expect. Your argument structure supports mutually exclusive claims, so it's an appeal to ignorance and a fallacious argument.
My DP, DD and I all have autism. We are all incredibly well behaved. When the conditioning and hard work begins to break down and we're struggling, we have workarounds and methods of dealing with this to avoid having a complete meltdown in front of other people. Inelegantly, the last solution is often to just run for cover and find a quiet space to deal with it away from other people.
Even in the worst case scenarios where the meltdowns happen and you can't get away to deal with it or you can't change the environment to prevent the trigger, from an external point of view, the meltdowns are pretty much a lot of flailing, panicking, stuttering, wandering around in circles and looking confused - punctuated with lots of "I'm sorry" because having a meltdown in front of people is one of the most humiliating, traumatic experiences possible for us.
Yes, there are times when we don't behave in ways NT's might expect. But the vast majority of times we are able to control it and successfully cloak because we've learnt to recognise and manage the triggers. When we can't manage it, we're not offensive, we don't demand that other people fix our problems for us and (in reference to the classroom drama queen thread) we absolutely do not concern ourselves with how other people are doing.
When we meltdown, it's because we can't deal with our environment as it stands. The over stimulation becomes unbearable and we're in survival mode. Believe me, there is absolutely no room in that maelstrom for competitiveness or trying to best someone else. We're literally trying to deal, nothing else.
So, honestly, I get what you're saying about "maybe there's another factor that's influencing the behaviour here". Yes, there probably is and we should try to be more understanding or accept that someone is probably just having a bad day.
But no. Please, please, please do not try to suggest that autism might be responsible for someone throwing a tantrum unreasonable. Autistic meltdowns do not look like someone being a diva or a drama queen. There's no well-reasoned rationalisations on why you deserve special treatment, there's no caring about how they look in front of other people.. in short, there's no goal other than finding the safe space.
But, to circle back to your argument:
Some people who behave in ways we do not expect are autistic. Some people who behave in ways we do not expect are horrible.
Some people who have autism are horrible.
Some people without autism are horrible.
And, for what it's worth - we're not stupid. We're as able as any NT to determine whether our behaviour and responses are justified and reasonable, or whether we're being demanding and unreasonable. If an ASD adult is being a dick and they can't help it, the most likely outcome is for them to disappear very quickly, then come back at some point later, full of apologies. Of course, they may just be a dick anyway - with or without the autism. In which case, the apology probably won't happen.
In the classroom thread specifically, this is not the behaviour of someone having an ASD breakdown. This is the behaviour of someone who wants something very specific and is in a clear mental space to intimidate and manipulate others to get what she wants.