Reality is perception.
Perception is reality.

But what exactly does that mean?
Perception is the way you view or see anything. It's what gives "definition" to something.
For instance, what exactly makes a red apple a "red apple"? Is it the color? Is it the fact that when you bite into it, it makes a crunch and is juicy?
No. That is the way in which you percieve it. After all, who exactly defined "red" as red? And who defined an "apple" to be an apple? Why dont we percieve it as being something else entirely?

The answer is that we ourselves give the various things definition. And from that, we all construct a larger "reality" in which we all consciously perceive together.

So again, what does this all mean?

That to control perception is to control reality. If say, the idea that red apples are not actually red apples, but are instead purple grapes were to spread, and enough people were to percieve it that way, we would no longer view red apples as being red apples. We'd now view them as purple grapes.

Think now the implications of this in a more practical scale. When the media broadcasts messages favoring a particular viewpoint, they are in effect influencing people's perception of those views, which in turn works to shape reality. Until eventually, we end up in the situation we are in now, where boys can actually suddenly become girls and craziness becomes the new normal.