In the United States I strongly suspect that at least one major political party's reaction to sulfur spraying would be to try to increase the production and use of coal and oil.

I suspect that this reaction would not be confined to the US.

We could end up in a situation where greenhouse gas levels in 50-100 years are massively higher than they are now, with heating being held in check by continual sulphur spraying.

It would then only take for something to disrupt the sulphur spraying for a year to have sudden massive warming.

It would make more sense to save sulphur spraying for after we are firmly on the road to zero emissions and have reached the point where it is not economically feasible to revive coal and oil. Then sulphur spraying as a temporary measure to lower temperature until our falling emissions make it unnecessary might be safe.