The interviewer could explore the impact of online fraud or identity theft or cyber-bullying, and look at how fast these problems have been growing in recent years. Then challenge the advocate of weakened encryption or mass surveillance over why they want to require security vulnerabilities or create huge databases that will make great targets for criminals. If they claim everything would be securely held and strictly for police use or similar, go with Snowden and Wikileaks.
If the advocate brings up their other favourite argument about protecting children, the interviewer could ask whether it's really a good idea to make it easier to intercept private picture messages between teenagers.
They could ask why the government wants measures that would inevitably undermine investigative journalism that holds the government and the police and the security services to account. Then start listing past controversies relating to the behaviour of those groups to demonstrate why that public interest reporting matters.
It's not as if privacy and security advocates only think these things are important because they don't like the government or something. There are real, serious consequences in play several different ways here.
