Because a few people repped me and asked me to clarify:
Ego is a holistic self-identity, and while its true that individual thoughts, feelings and beliefs arise from this definition of self, to say that feelings and ego are interchangeable in this context is incorrect. It's like saying that the momentary sting and disappointment you feel from getting a minor paper cut is the same as your definition of self as someone who does not get papercuts but would probably deal with them just fine if he did get one.
Feelings are short-term reactive mental states. They can be mediated, compartmentalized, dismissed, or otherwise acted upon by other facets of the self. When not resolved, sustained feelings become moods, which can inevitably progress into temperaments before eventually becoming absorbed into the ego as permanent beliefs or personality traits. Where butthurt is concerned, this progression usually happens when the ego is unable to provide the tools to effectively to defend itself from or reconcile those initial negative feelings with its own beliefs and therefore those feelings overstay their welcome.
I've observed that a propensity toward butthurt is typically found in people with a very narrow frame of reference, be they feeler, thinker, intuitive or sensor. The smaller their worldview, the fewer perspectives they have on being able to reconcile challenges to their beliefs. For example, if you spent most of your existence playing video games, you're probably going to take someone challenging your gaming abilities a lot more personally than someone who has other ways of occupying their time.