Emotions are indeed very important in building our opinions. We think of ourselves as rational but are often more driven by our gut-level attractions and aversions, drives and fears than we realise. I recommend Drew Westen's book 'The Political Brain' in which he explores what MRI scans reveal about our political 'reasoning.' His neurological research suggests that:

"None of the circuits involved in conscious reasoning were particularly engaged... Essentially, it appears as if partisans twirl the cognitive kaleidoscope until they get the conclusions they want... Everyone... may reason to emotionally biased judgments when they have a vested interest in how to interpret 'the facts"