Cansu it's very difficult, very. Nor do I think Katy meant that all it takes, for a child with ASD to behave, is to put in firm boundaries.
A year ago, I went to a behavioural workshop where the present worked with a lot of teenagers/adults on the Autistic spectrum. He quoted that quite a "few Autistic teenagers/adults are in prison". He didn't believe that we shouldn't teach our children the appropriate social skills/appropriate behaviour because they have ASD and well all these behavioural challenges comes with it. Like he said... "when the child with ASD becomes an adult, and has to function in the world on his own and commits a crime (which is the majority of the time not out of anger but due to unmet needs....) the law would trial him as an Adult, taking very little account of his ASD". I'm not sure how this is true.
I didn't think the OP was being unreasonable, I do think it's our jobs as parents to teach our children...even more !social skills/ what's unacceptable behaviour... this may not be done in a conventional way (telling off a child, reprimanding them) ... it could in a form of using a social story, modelling appropriate behaviour, get the child to express their feelings (either using emotion cards, Makaton, talking about feelings and how other people feel if they do XYZ...targeting sensory needs/sensory inputs.
I say this because as the children get bigger and stronger, I fear that it would be even more challenging to handle, so it's good to put this in place now rather than later.