Once upon a time, I think I would have said yes.
But these days, I've read a lot about how the sales of illegal drugs imported into the UK fund organised crime, human suffering, slavery, drug wars, etc. How the West's desire for nice neighbourhoods and illegal drugs causes masses of suffering in the countries that supply it. About Narco-states. The stuff I've read was mainly concerning cocaine, but before I did any reporting I'd read to see whether the same issues were associated with cannabis production.
If they do, then... I think that I might much rather the local spliffheads gave their money to some guy who grew the stuff in England, without slave labour, and spent the money at Tesco, even if he didn't pay tax, than they funded organised crime cartels in other countries, who were involved in sex trafficking, murder, torture, and all the rest of it.
I'd like to know a lot more about his customer base before I made the final call, for obvious reasons, but if he does actually have any scruples at all and he's working on his own, human suffering caused by drugs would remain the same in the UK after he went to prison, because local users would just find another dealer,but suffering in the rest of the world could increase.