In can be very difficult for someone with autism to communicate because, in addition to the communication barriers that everyone faces every day, we have the autism communication barrier. The barrier is different for every individual on the spectrum. We might take statements literally, not read sarcasm or irony, and we might not see humor in the same way that others do. Through our black and white thinking, we may have trouble comprehending situations where there is more than one correct answer. In other words, we expect there to be a clearly defined right answer and wrong answer for everything. Even though I am armed with that knowledge through experience, it is still difficult to handle situations where there is considerable gray area involved, such as controversial topics and political topics where there are strong conflicting viewpoints.
In addition to that, there is the sensory issues to consider. I have heard that when individuals with Aspergers Syndrome are very focused on what they are doing, they might be completely unaware of what is going on around them. To my understanding, they can literally be deaf to everything around them and only see what the task that they are preoccupied with. In some cases when I am dealing with a sensory overload, I might stop listening to someone who is speaking in order to deal with the overwhelming sensations. Someone with moderate to severe autism might be so caught up in the swirl of sensations that is their reality. They might be completely unaware of what is going on around them. All their actions are based off of reactions to those sensations that dictate their reality.
This description is by no means exhaustive. What I have tried to give here is a brief overview of what I consider to be the autistic communication barrier. Some of those are communication barriers that I encounter in addition to all the other communication barriers that exist between genders, nationalities, and even sub-cultures. While communication can be difficult for everyone in some situations, try to keep in mind that those with autism are dealing with extra barriers in addition to the difficult barriers that everyone experiences in this diverse world.