Hi Sheena -
My DH is still coming to terms with DS and his autism; DS turned 7 this month. I think it's sometimes harder for men than women to deal with autism when it involves a son. It's that whole "mini-me" thing and to know that our children are not neuro-typical is a hard pill to swallow sometimes.
Maybe DH would be OK with the shirt if he could realize how much it would help you in dealing with people who truly don't know any better about your son. Once you put it out there, most people respond with compassion and patience.
Hugs to you......hope things calmed down at home!
Wife to an awesome DH and Mommy to an adorable DS who is on the spectrum for autism