Well I believe they ended his life because that is what he wanted, not because he had autism. They thought maybe they could make things better for him, so that maybe he would want to live, and that failed.
I watched an assisted suicide documentary that took place there, and they made very sure that that was what the person wanted. Like "if you drink this, you will die, do you understand?" Person clearly acknowledges they understand. "Are you sure?" again the person says yes. It was a very thorough process.
On the flip side, would it not be wrong to keep someone from doing this because they have autism?