Weird! I wonder why there's such a difference in our experiences.
I also don't think making it psychologically hurt is going to make any difference, especially not when you're asking them why their fellow countrymen shit in the streets. Based on what I've heard and read, a lot of them justify their work by villainizing us in their eyes. Which isn't unfair! We're vastly richer than them, and they don't see any particular problem in what they see as being a Robin Hood-like character. Insulting and abusing them just further justifies their actions in their mind.
I used to try to waste their time as well, but after I postulatede my prison-work theory, I no longer do that - they don't have a choice, and it's cruel to put them through that.