Religion

The OP refers to the correlation of religion and violence. Poverty and average height may or may not be contributing factors, but introducing them for no good reason doesn't further discussion much.

Here's a more relevant question. China is frequently provided as an example of the intolerance of atheism, as if either or those things is a causal factor of the other. Another way to look at it is China is a country with more than 4 times the population of the US with roughly the same land mass, yet is far less violent than the US. So let's say China suddenly became more tolerant of religion and as a result became more religious. Would violence be positively or negatively affected? So maybe there's arguments for either, or another that says there would be no effect.

Now consider Thailand. Culturally it's very similar to China. Poverty is greater than China, but not by much. On the scale of totalitarianism they aren't that far apart although Thailand is clearly more so. Religion and violence are pretty much diametrically opposed. So is there a causal factor between the two? Perhaps not, but ignoring the possibility doesn't make much sense, and whether you do or not there's still no shortage of people who argue religion must be assumed to be a positive influence on society with pretty much no evidence to support that assumption and at least some correlative evidence which suggests otherwise.