I've only recently become aware that I probably have Asperger's (all signs are pointing to yes), but I figured out about a year and a half ago that I have gluten and casein intolerance. Considering it took me so long to figure out what was wrong with me--in terms of my diet--I can't say whether my development, personality, etc. would have been affected one way or the other if I'd been on a GFCF diet all along.
In my experience, consuming gluten and/or casein did/does not produce morphine-like effects. They both make me sick, enough so that I am afraid of gluten and never eat it (not on purpose, anyway), and I sometimes eat cheese/consume casein in very small amounts but suffer the consequences pretty much immediately. I have neurological effects from gluten--severe anxiety, peripheral neuropathy, facial numbness, migraines, lightheadedness, and vertigo. All those symptoms went away when I quit eating gluten. They return if I ever accidentally eat it (along with digestive issues, but the neurological problems are far worse).
I've heard that people often crave foods that they can't digest or have an intolerance to...so maybe that's what you mean by morphine-like effects, but I'm not convinced that eating bread is on par with a morphine fix.
But should a GFCF diet be mandatory? Of course not. If it works for you, great. If not, eat what you want. Personally, it saved my life. I can't say how any of this relates to Asperger's, or if it even does (I'm still weird, even on a GFCF diet!), but I know that for me, gluten is like poison and I'll never willingly eat it again.