I was at a nearby garage sale recently. I started talking to the couple about detecting there. The mrs was amenable but the mr said "oh no, I've seen what you guys find, I'm getting a detector myself."
I offered to share my extra detector and tried to chat a bit with him, but the whole tone of his response was that he thought his yard was full of treasure. The "I've seen what you guys find" told me what he had been watching on TV.
But on the upside, I keep in mind that these shows are not widely watched by the public and I don't let a response like that dissuade me from approaching someone else. The detecting shows are on smaller cable channels and the percentage of viewers compared to the population is extremely small.
As Songdog said, these shows also bring a lot of people into the hobby with no instruction and often no desire to dig it right. After a few hours at the old park in town, a few modern coins, and a ton of trash, the delusions of riches are gone. But the divots and scarred landscape they leave behind live on to be discovered later by park personnel. And I guess we all know what the kneejerk city gov't response too often is. It's much easier to solve the problem by banning detecting than try to go after the actual culprits. Tell everybody no and you don't have to worry about anyone spending time figuring out who is damaging the grounds and who isn't.
Unfortunately, the shows aren't going away.

I know Diggers had good enough ratings to be renewed for a second season, so the viewers are there. I hadn't heard of the show Gary mentioned, but in last month's W&E they mentioned a new one later this year with Bill Ladd called Dig Fellas.
Let's hope this TV trend runs its course soon...