One question I would ask from this interview would be :
How are we sure that extraterrestrial activity could be monitored by a physical quantity such as electromagnetic waves?
I would not doubt it if extraterrestrial activity could only be monitored by something beyond the physical realm.
I had a similar question when I was watching the Tarter interview as well! It seemed a little odd to me that people thought that, out of everything, EM radio waves would be the method through which we would be able to communicate/discover ET activity. Radio waves have been used for communication for over a century now, and I found it hard to believe that if we are to make contact with ET societies/organisms, it'll be through something as physical and, relatively, simple as EM waves. Maybe it is possible though, but I'm also skeptical of us being able to monitor ET activity through basic physical means.
https://www.labxchange.org/library/items/lb:HarvardX:68789c56:lx_simulation:1