Sam is one of my favorite public intellectuals. I made a video looking at popular level objections to value realism. I hope it is okay that I included Sam in it: https://www.youtube.com/watch?v=oDE6e6TEGos&t=447. I intend for my references to Sam to serve his work.
The link took me straight to about 8m into the video and you mention Sam Harris as an example of a proponent of reason and evidence. I don’t think you need any permission just for this (as it is an opinion about a public figure based on publicly-available information from and about them, and it is hardly a deliberate misrepresentation or damaging libel), unless you end up quoting his writing or podcasts verbatim at length without any acknowledgement and claiming the content as your own, which might be a copyright issue.
If you want to say something like - “in his book (insert title) Sam Harris claims that abc=xyz (insert argument). Let’s examine that - unlike Sam, I believe that actually xyz=abc (counter-argument), for the following reasons ... etc. etc.” This is all fine.
In general if you want your work to be credible and authoritative it is always useful to acknowledge sources somewhere even if not explicitly required. It shows that you have undertaken good research, it also demonstrates your respect for other sources of information or opinion, and also allows readers who are interested to follow up with reading and research of their own. So if you for example based some of the reasoning in your video around specific arguments in Sam Harris’ book or books, even without quoting directly, it would actually appear more scholarly and thorough to mention this source in your footnotes (somewhere in the introductory text below the video, or in the credits perhaps).
Kalessin, great comments, thanks! I’ll take that into account!