I wouldn't call it childish to have such a conception, but rather an indicator of ignorance. Please note that I do not mean that in the insulting tone, but in the literal one. When we do not know something, we are ignorant of it. I would simply say that you were ignorant to that fact.
The government's role is not that of a protector of people, but instead a protector of its own autonomy. That is, government carries out a means of control (law, tax, policy, decree, etc.), and protects its ability to control from threats local and foreign. That is completely independent to the wealfare of its citizens.
The ideal of a government having a role in the safety, welfare, health, or interest of the citizens it controls is bizarre. It's a view that presumes goodness in group, where there is no indication of that ever being the case at any point in human history. It is, in a more disturbing and worrying light, a view that reassigns the government as a kind of parental figure, when it should be abundantly clear that nothing of the sort is the case. It would be like a newborn chick, presuming the snake in its nest a protector, instead of a looming threat. The issue is, leaders are paid to lie and assure citizens of the opposite. Without a great amount of personal investment - or first hand experience - some may even start to believe such tawdry, grasping hisses as fact. The actions of such a cabal is apparent once it is measured.
Ignorance to that does not make you stupid, or childish, or any other number of things. It simply means that you did not know, what you later learned. From the sounds of it, this is a thing that has bothered you, and I am sorry to hear that it has weighed heavily on you. Just keep in mind that you are not alone in this sadness. It is a thing that may pass. Just keep in mind the facts of the situation you are in, and that anyone - ANYONE - who claims to do whatever "needs doing" to be in "the public interest" is most certainly one who moves about on their stomach.
On a related note: It may be beneficial to point out that, in a similar vein, police officer have no legal responsibility to protect citizens or their property - their role is not of protection, as some sort of "public utility bodyguard", but instead one of law enforcement. This is a slightly more nebulous point, as the so-called motto of law enforcement (in America, at least) is "To protect and serve". The fact of the matter is that it has been affirmed in SCOTUS that no law enforcement officer will be held responsible for failing to act to protect a citizen, even to the point of grevious harm or death. Laws are far more telling of the reality of the thing, than any non-binding, hopeful motto. A motto is merely a desire of public perception.