Rage and entitlement are expressions of extreme unappreciation for your parents for all the money, time, and effort with which they have blessed you.
That is assuming the parents did, in fact, provide a lot of time, money, and effort...
Of course any parent who would venture onto this site would care about their kid's future. Many parents really would never waste such a moment, and so many, if not most, of the parents here simply cannot relate to parents who choose not to help their children. In fact, there are some parents out there who are envious of what their children did with their lives, and such is why they refuse to pay. They feel that their children should struggle as much as they did, or that they don't deserve more than they had, which could be very, very little. Some even feel that if their kids are successful, they owe them a whole lot of money. Remember, you don't have to be caring or giving to become a parent. Just a reproductively functioning being.
I see my parents blow money like it grows on trees, on things they shouldn't be - such as drugs, cigarettes, and alcohol. So I can't help but harbor some resentment, especially when my dad tells me how stupid I was to spend money on college.
Sure, parents aren't forced to pay for your college, but there is something fundamentally wrong with assuming that they will (FAFSA). There needs to be more affordable, respectable choices other than community college for kids who have parents who will not help at all. Of course, this is difficult to prove and paying parents could easily "refuse" to pay so their kids have cheaper options, but perhaps this would be best in the long run to lower costs altogether.
Overwhelming rage is probably not a normal response to this situation, but some resentment is. It goes away with age, especially once you get a job and move out and on with your life.