Yes and no. At least for the US Constitution, all of it can be rewritten through the amendment process. In fact, one could call a constitutional congress and chuck the entire constitution out the window. We keep those protections in place because we don’t trust ourselves, in a sense. We recognize that the majority can trample on the rights of the minority, and that any majority can become a minority at any time. Therefore, we set out rules ahead of time that we adhere to even if it is inconvenient to the majority. It’s a bit like not allowing the rules of a sport to be changed by the leading team during a match.