Firstly I'm not a chemist or global warming expert but I've checked and confirmed that ammonia can be used as a fuel but the combustion process is probably more difficult than for petrol or diesel. And it seems to me that it is not as environmentally harmless as that video suggests.
When ammonia (NH3) is burned in air, my limited knowledge of chemisrty suggests the byproducts would be water (H2O) and various oxides of nitrogen (NOx). These oxides are already recognised as greenhouse gasses and contribute to global warming in the same way as CO2. Do some searches and reading on the internet - it's not new or revolutionary.
While using ammonia as a fuel may be cheaper than petrol or diesel, I doubt if it should be described as green. Replacing carbon emissions with nitrogen emissions is certainly decarbonising but that doesn't mean stopping global warming. I've no idea if the nitrogen oxides are better or worse than CO2 for global warming, but it is not zero emissions.
Aside from the conspiracy theories, the video strikes me as a bit like a Groundhog Day spoof - I can picture Bill Murray doing the interview. Was it released on 1st April ?