As I was reading through the comments I found a comment where an obviously loving mother spoke of how she had to speak for, on behalf of, and in place of her autistic son who does not speak. There are a couple of ways to take that, but just in case it was in the less positive way, I went ahead and offered some thoughts. I think you all may find them helpful as well. Here's what I said:
"I really hope that in your comment, you meant that you use his communication (behavior is communication, you don't have to speak to 'say' "No, I don't like that!" even if it's in the form of screams - even self-inurious behavior is communication), your instincts as the person (other than him) who knows him, and the words of autistic people as your guide. I think that's what M means, and certainly what I mean, when we say you shouldn't speak for others. That you shouldn't try to claim that, in this case, your child's experience is the same as everyone else's, and applying this further, nor should you speak in place of someone - which is what you would be doing if you spoke and said he wanted something that he was clearly communicating through behavior that he did not want, or ignored the words of autistic advocates.
Basically, you want to amplify what you think your child's actual wants and needs are, amplify what you think he would be communicating if he could, rather than speaking for yourself and saying that's what he would want. I hope this makes sense - here are some examples of what I mean.
Example of a parent who speaks for their child:
Example of a parent who amplifies their child (her daughter is communicating by writing now, but you can look back further in the archives if you want an example of a time she wasn't):
You have a very difficult job, indeed. Parents in your position have to struggle to think of what their child's wants or needs might be, even if they might be different from their own instincts. I can't imagine how hard that must be. But you shouldn't have to do this completely on your own. Whenever I have questions about what an autistic child who can't communicate their needs to me would want, I turn to WrongPlanet, an online discussion forum for autistic people, and I ask them their opinions. There are people all over the spectrum there with all kinds of diverse experiences, and I use their input, combined with what I personally know of the child, to come to my best guess conclusion of what I think they would want. I'd really recommend checking out the website, it's extremely helpful.http://wrongplanet.net/
You sound like you love your son very much and I wish you both the best of luck."
I hope this was helpful for you ASE readers as well. I really do use WrongPlanet a lot as a place to ask questions - they have a parents page where you can ask for others' insights and it's really helpful. If you're shy and worried about posting, they archive their old posts so you can simply search through the website and see if someone has asked your question before.
As always, remember I'm not a professional, I'm just a family member writing from personal experience.