The journalist was right to challenge him if the claim was BS but I disagree that asking him to drink a glass of roundup and him refusing is a good argument. I mean take the position of the Monsanto lobbyist, he most likely never attempted such a stunt before, he doesn't know how it tastes, he doesn't know if drinking a whole glass of it at once is going to cause digestive distress etc... Of course he's going to refuse even if he's honestly convinced that he's telling the truth.
Good journalism would've been to show how his claim is bullshit by citing sources disagreeing with the statement. But that doesn't make for good TV.
Also I disagree that the claim was that glyphosate was "safe to drink" like a soda or something, rather he said that it wasn't going to hurt you which is IMO not exactly the same thing, especially in the context which was that glyphosate was accused to cause cancer. I'm sure you could eat few spoonfuls of salt and it won't hurt you, I still don't advise doing it.
At this point I might sound a bit like a Monsanto lobbyist myself and I assure you I'm not, I'm just a bit annoyed that these types of stunts seem somehow more important than rational discussion and scientific studies. This guy is not even a Monsanto exec like claimed by the parent. I guess they revised their scripts after that.