Is private property justifiable?

Is private property just something made up by men and defended by libertarians, in order to suppress the working man and allow the cruel and greedy capitalist to prosper? Is private property just an instrument made by man and upheld by man, and not really justifiable with logic and reason?

Of course not. There are many brilliant logic for private property, and none against it that hold. One can be found here, and is a new one in the eyes of this author. The following is a quote:

Because rights in one’s own body have been established, property rights may be established by building on this base. This may be done by pointing out that rights in one’s body are meaningless without property rights, and vice-versa. This can be illustrated by the following example. Imagine that A, a thief, admits that there are rights to selfownership, but that there is no right to property. But if this is true, we can easily execute A simply by depriving him of external property, namely food, air, and/or space in which to exist or move. Clearly, the denial of a person’s property through the use of force can physically harm his body just as direct invasion of the borders of his body can. The physical, bodily damage can be done fairly directly, for example by snatching every piece of food out of a person’s hands (why not, if there are no property rights?) until he dies. Or it can be done somewhat more indirectly, by infringing upon a person’s ability to control and use the external world, which is essential to survival. Such property-deprivation could continue until A ’s body is severely damaged, implying that physical retaliation in response to a property crime is permissible, or until A objected to such treatment, thereby granting the existence of property rights (for this can be the only grounds for his objection to being denied property). Just as one can aggress against another with one’s body (e.g., one’s fist) or external property (a club or gun), so one’s self-ownership rights can be aggressed against by affecting his property and external environment.

So, sure, private property can be looked upon as a mere instrument of man, but then the same must apply for food, clothes and general survival. Survival is surely an instrument of man and can be removed or disposed of. Sounds like that which happened in the planes of Ukraine during Soviet Union supervision of one of the most fertile areas in the world.