Yes, we know what the event was and pulled from your link:

“In her speech, Harris discusses how young people can be prone to making bad decisions and how the program can help those who were arrested on low-level charges by having charges dismissed after completing the program. In the video clip, the audience laughs at Harris’s comment, further indicating the nature of the comment is facetious and not quite as implied by the standalone clip as shared in these claims.

She called that age group “stupid”.

Facetious: adjective
treating serious issues with deliberately inappropriate humor; flippant.