The difference is that other things also tend to justify government power.
If we were to use your logic, the fact that there exist companies susceptible to market failures would mean that we should get rid of corporations entirely, even though there are valid reasons to justify the creation of corporations. The conclusion is absurd because the logic is absurd.
Similarly, the conclusion that markets efficiently allocate economic resources does not lead to a conclusion that markets can, by themselves, fairly allocate other types of resources (to say nothing of non-resource allocation functions of government).
Instead of looking at a bad government and saying that the problem is government, you need to look at the bad government and realize that the problem is that it's not good government, and then fix the government to not suck. I won't claim it's always easy but most things worth having are not easy otherwise everyone would already have them.
If we were to use your logic, the fact that there exist companies susceptible to market failures would mean that we should get rid of corporations entirely, even though there are valid reasons to justify the creation of corporations. The conclusion is absurd because the logic is absurd.
Similarly, the conclusion that markets efficiently allocate economic resources does not lead to a conclusion that markets can, by themselves, fairly allocate other types of resources (to say nothing of non-resource allocation functions of government).
Instead of looking at a bad government and saying that the problem is government, you need to look at the bad government and realize that the problem is that it's not good government, and then fix the government to not suck. I won't claim it's always easy but most things worth having are not easy otherwise everyone would already have them.