"The first principal is that you must not to fool yourself, and you are the easiest person to fool". R.P. Feynman
If you hang around cannabis users at all, you're probably familiar with the idea that it helps people to gain insight into themselves. Authors such as Carl Sagan and Michael Pollan have articulated this effect in great detail.
Another of cannabis' well known effects is that it gives us courage. Maybe the stories about ancient Islamic soldiers eating hashish and the word assassin being derived from the word hash are myths, or maybe not. In any case, it's quite obvious that it does give us a certain specific kind of courage. I would describe that flavor as 'courage to self reflect'. In this day, we generally assume that self reflection would help a person be more peaceful. But, maybe in those ancient times, self reflection could lead you on a path towards (necessary) violence in the form of assassination. It seems like an unlikely path now, but times change.