I think a lot of people are missing the point. A higher demand for hydrogen will incentivise companies to improve the production methods for hydrogen, hopefully with a more conscious effort to keep it green, i.e. Improving electrolysis methods.

Nobody is claiming that all hydrogen is greener than diesel, the point is hydrogen has the potential to be vastly greener than diesel, and the best way to explore that in a capitalist society is to increase the demand for it.

A small disclaimer, I know nothing about hydrogen.