YouTube is a 3rd party platform that is not owned by Frontier Developments. If you believe someone has breached YouTube's Community Guidelines, you should look to report the matter to YouTube.
YouTube provides clear guidance on how you can report content in the Reporting and Enforcement section of their Polices and Safety page.
If you are concerned with the conduct of a player of any Frontier games including Elite Dangerous, direct YouTube URLs and timestamps can be used to provide secondary supporting evidence for your report to Frontier.