Should I have him retested for autism because of others doubts?

My son was diagnosed with Autisim in Feb of 07. This was a 6 hour long ordeal at "CARE" Carolina Autism Resource and Evaluation Center and he was tested above the minimums in all of the different tests they use to diagnose autism. Well, prior to his diagnosis and now over a year later I have people like his speach therapist and occupational therapist telling me that they just don't think he is Autistic. This frustrates me because I dont want to make excuses for his behavior or label him something he isnt. Elijah has come a long way since he started therapy when he turned 2, he is now 4 and he communicates very well and plays fairly well. These are SOME of the things he still has problems with... Fits, he throws his body all over the place! He will throw himself into walls, off chairs, out of buggies... anywhere really! He echos back questions when he isnt familiar with them. He stems sometimes. Attached to certain toys or objects. I'm out of character spaces, what do you think?