There are many different ways of communicating and interacting with people on the autism spectrum, it takes care and commitment and also a very specific person centred and empathetic approach to get into their world on their level of interaction and communication. There are sometimes many walls to and layers one has to understand and respect when working with people with autism.
Imagine a castle that is the core of the autistic person this castle represents them as a mental and physical self, within the castle are all there strengths, difficulties, sensory issues and most importantly their personality.
This can happen when the castle is being threatened by an army of people that want to hurt it this army can represent sensory issues, communication difficulties, negative environments, people and places, the individual or individuals interacting with the autistic person not understanding the autistic persons personality or communication profile. This will cause the the castle (person with autism) to raise its defences in certain ways to deflect the oncoming barrage of information and try to deflect the negative energy coming towards them.
If the individual understands the person with autism, researches about the castle and its qualities, difficulties, sensory issues and personality with trust, care, empathy and understanding the castle will have no need to defend itself. You accept the person for whom they are and you will not be perceived as a scary on coming army but a individual whom the autistic person can be themselves! That will make them happy for if a person can't be themselves whom can they be?