Autism thing?

I wondered if the following situation is commonly experienced by other autistics?

I am out in public, walking along, minding my own business, and some random stranger says, "Cheer up, it might never happen", or words to that effect.

I find it very intrusive and usually cannot find anything witty to say, which would be an ideal response. I am hugely resentful of the concept that I owe it to complete strangers to compose my facial expression to suit their peculiar standards.