My reason for vegetarianism is, at its core, a very simple one. I'm horrified of violence, almost by default. And I tend to be extremely empathetic. I'm emotionally motivated to treat animals with kindness before I am intellectually motivated. The discrepancy in lw might depend on personality differences. Or sometimes you can get very bogged down in the intellectual minutia trying to sort everything out, and end up reaching a plateau or inaction (i.e, the default).