The fact that people believe in something does not make it real.

The belief is real. It is very important, because, true or false, these beliefs have real consequences.

just because a bunch of people think they are really girls when they are boys or the other way around does not make it real.

Again, the belief or feeling is very real. As to whether it is true, your childish remark about chromosomes some comments above strongly suggests that you should learn very very much before you even start to assess this (did you even know that there are people who look like women, think of themselves as of women yet are genetically men?).

The idea of private property is not a social construct, even animals mark territory and defend it as their own

Some do, some do not. This does not mean that idea of private property is not a social construct, or that it is an evolved one. From what we know about so called primitive societies, their idea of private property, if at all existing, is very different from our western one. You should really do some learning.

The fact and truth is there is only male and female, everything you

The fact and truth is that you lack basic knowledge beyond high school level, not only in anthropology, but also in quite elementary biology and anatomy.