... I'm not even saying he really believes it. What I asked was, are you comfortable with a POTUS acting like this? How is this helpful to anyone? How do to the citizens of USA benefit?
Let me give you my perspective. For the record, I vaccinated my child, and believe in vaccinations. Autism, vaccinations, and anti-vaccination movement are all very serious matters alone, let alone in combination. The anti-vaccination movement, right or wrong (and I do believe they are wrong), can not be easily dismissed. What needs to be done is to dissuade them, not simply dismiss them. That starts by listening to and acknowledging their concerns. Humans are hard-wired to look for cause-consequence in anything new or bad happening (e.g., the rise in autism). In that anecdote about an autistic baby, I believe he ended it with “Is there a link? I don’t know” (citing from memory).
Trump is a laymen in many areas, bar real estate development. That puts him on an equal footing with many among his constituents. That’s part of his folksy charm. People can relate to that. So, when faced with a mother with an autistic child, he can react to that at the same layman level, acknowledging her concerns as a minimum. Or he could label her as an ignorant deplorable. Well, we’ve seen how the latter worked for a certain presidential candidate.