Hayek claims that the State should step in to force people not to compel others to do what don´t serve their purpose, but then his argument is flawed, since that way the state is a coercer agent itself.
The fact that you know the rules a priori doens´t make it right or morally good.
Two comments about the above/your writing:
1-) By using the vague "it´s the argument of Hayek..." doesn´t make it clearly expressed, one might wonder what argument is it, I for the sake of example offered one, but certainly it is not the one you meant, read or was discussing.
2-) When writing academical texts/essays, we usually soften the language. Thus we don´t say straight out state that it/something is "uma besteira", so I used the "flawed" word. Other words or expressions could be used, for example "I don´t agree with him that..." etc.
A thesis elsewhere has it that "My thesis is that, from a moral point of view, Hayek’s critique of social justice Nonetheless fails." and then he go on to the reasoning of why (he thinks so).
It´s some of a Brazilian tendency, or that of some professors and top brass intellectuals to express themselves in no incertain and impolite terms. That doesn´t help further their ideas, it may not hurt their fame as well (at least in Brazil). But when writing essays and thesis, we should go by the books.