It's not impairing for me, but I do agree. While it's not impairing for me, it can be to people without prodigious tolerance.
The method they proposed using to test for it though is not a good one, 5 nanograms of THC is way too low. Like you saw, there were two people in that group that were higher than 5 nanograms & they hadn't even smoked that day. Those levels can also vary depending on certain factors like body size & things like that. It will be a difficult task to come up with an efficient & accurate way of detecting if people are medicated or not.
The only thing it does is make you go a little bit slower... Also thats because most people are paranoid. If it was legal then people wouldnt be paranoid.
What this individual Fox News affiliate did is awful. Has "Fox News" responded to this? The response of the "Fox News Channel" will help determine their credibility.