Click the flag-as-offensive icon next to the message.
Within seconds, the message will disappear from everyone’s view.
The streamers & moderators will be alerted of the message. If they choose, they can delete the message permanently, ban the person who asked it, or mark the message as safe & appropriate. If they do mark the message as safe, the message will show back up, and not be able to be flagged again. (This is to prevent people from abusing the flag feature.)