I mean when you consider Guwon's circonstances he really just has the mind of a child that doesn't know right or wrong... And even then, the rules that he made up look like they were established based on trial and errors like... he realized how important drugs were for the town in the past so of course who would want a shortage of those in dire circonstances? I mean between the life of a child that isn't really useful at the moment and the probability of a hound/villager that is essential to the town needing the same medicine in the near future, the choice is evident... especially if it's like the last stock of medicine... in dark times, dark decisions have to be made.
While the punishment of being beaten too death might have been a bit too much for the crime, it could also be explained if in the past there was lighter punishments and people were not scared of it and did not respecting the rules in consequence... I mean we have prisons in our society for a reason but I imagine that during the apocalypse why would you want to take care of a prisoner when food is scarce and you'd need dedicated facilities/surveillance for him? So instead eliminate the guy and make sure that everybody else learn to not make the same mistake so... ╮( ̄▽ ̄)╭ the public punishment makes sense to me.
Now, while he may consider Teach's opinion on right or wrong rules/decisions, I can feel that feels will go down like... can the rights and wrongs applied in a normal society even be applied the same way in an apocalyptic world? I doubt that... He's probably gonna listen to him and shit's gonna go down ( ̄へ ̄)