One argument for the permissibility of stealing rests upon the claim that our economic system is fundamentally unjust, and that theft from the government, employers, insurance companies, and so on can at least slightly relieve some of the inequalities created by the unfair economic advantages these institutions possess. the basis of this argument seems to be:

The basis of the argument seems to be that economic inequalities are caused by one economic sector stealing from another.

Explanation:

This argument rests on the explicit assumption that government, employers and insurance government are thieves, and this is the means which allows these sectors to increase their wealth. (assumption mentioned in the answer) People who think this is the case think that increasing capital is accomplished by working only for the benefit of those who create money. Therefore, some people argue that is is permissible to steal from these sectors.