In the early days (dd1 was diagnosed at 2.5, and we had been in the system since she was 20 months old, so they really were early days!) dh was firmly in the "she'll catch up one day" camp. Initially dd1's problems were a huge speech delay, so I could see where he was coming from, but there was more to it - lots of everyday stuff that he didn't see as he was out at work.
It was very hard, being surrounded by people whho thought I was being, for want of a better phrase, a pushy mum. One who wanted more form her child, and wanted it now, etc. Even the hv's I was talking to at the time kept dismissing my fears ("she plays on her own for an hour without missing you? that's great, you must get lots done around the house" - dd1 was 8 months old )
dh did come around, and surprisingly easily. From the very first (useless) appointment with a community paed, he was more onside because he could see that the paed was talking nonsense. When the report came through, he read it, and pointed out several errors. So he pushed for the next appointment because he wanted those eroors rectified (not quite the same reason I wanted the appt, but at least we both agreed we should see someone else)
He still had days where he thought everything would be ok, but it is natural to hope for the best.
We have lots of problems with extended family still. My PIL think dd1 will grow out of her autism. My BIL (and their families) cannot cope with the fact dd1 is disabled, and only see the problems, not the good side.
It is very hard, but every day it gets easier, because we are not the ones in the wrong here. They are.
I was at a party with some old friends at the weekend. One I hadn't seen since I was pregnant with dd1. Dh spoke to him first (I was occupying dd1 & 2) and obviously brought him up to date with our news. When I saw him, literally the first thing he said was "so, how disabled is dd1? that must really affect your life". No hello, no catch up on other news. All he could see was that we were affected by disabiltiy. Some people are like that, and it's their loss. He won't ever know dd1, but only he loses from that.