It's all about human nature basically and nobody likes having someone pass judgment on us,especially by strangers.That's why we get offended and bent out of shape as it's like how can they think they really know us when they don't.
We all judge each other from our own point of view, but why is it that we get offended so easily? Why can't we just take in their opinion and just forget about our feelings for once?
In order for someone to truly believe something there has to be an emotion behind it. It takes practice to learn how to keep your feelings about it to yourself and allow others to feel the way they do. It's natural to want others to share feelings. Learning that self control 'should' be taught during childhood. Unfortunately that's rare for kids to learn as an adult with little self control is going to have a hard time teaching a child self control, and so we end up with a large portion of people arguing over differences.