I think this is a very good question that can be looked at in a variety of ways. In my opinion, I do not see anything wrong with Debbie Purdy's husband assisting her with her death. The way I see it, if it's what she requested, and was what she wanted, I don't have an issue.
As a society, we are in general more kind to our animal friends than to our own loved ones who are human beings. Someone could have a terminal illness and have no quality of life at all now or in the future and we would not help her die. This was the right decision.
Although British courts were right to allow Debbie Purdy's husband to assist with her possible euthanasia, Purdy is still alive and hasn't yet decided to end her life. A victim of multiple sclerosis, Purdy has campaigned for more open assisted suicide laws in Britain and won her case in 2009. However, in 2012, Purdy postponed her plans to die as she remains in a wheel chair and is losing her hearing. Purdy should have her loved ones nearby when she dies, and the courts decided rightly that her husband shouldn't be held accountable for her death. Purdy clearly knows what she is doing, and who better to assist in her death than her husband?
When people suffer from illnesses to a point that it makes them not feel it is worth continuing, they should be allowed to die on their terms. It's obviously a very sad subject, but there's nothing moral about forcing somebody to keep living when living is torturous for them. Morally, it's best to let them say when they've had enough.
Given that Debbie Purdy simply needed relief, I believe it was perfectly acceptable for the courts to allow her husband to assist her death. Purdy's case was handled for future problems, so she could ensure that her husband would not be arrested for helping her. Purdy is a prime example as to why physician-assisted suicide is sometimes the most moral answer to a medical issue.