To laugh at someone with scorn is to scoff at them. People have scoffed at many great inventors, saying their products would flop because the public wouldn't be interested in things like the light bulb, the personal computer, or the pet rock.
The verb scoff is often followed by the word at ("scoff at the idea, scoff at the statement, scoff at the notion"). The verb can also mean to treat with contempt or to mock. Naysayers scoff at all kinds of theories, and grouchy old men tend to scoff for the heck of it.