No one is an English idiom meaning "no person" or "no body". It is the opposite of "someone". It means "no one who counts or can be heard or respected" or more closely "zero persons that we are concerned with," whoever "we" (those making the statement or agreeing to it or thought to do so) are.
It literally refers to "zero persons or voices". But this is not always exactly what is meant. It does not usually literally mean that absolutely no human on Earth can be found that expresses the view or takes the position that "no one" takes. It means that the view or position can be safely ignored, and that those who take it can be singled out for social exclusion.
So, for instance, it can be said that "No one in the United States supports communism." But of course there are a few such people, they are just not open or declared supporters, or not found, or they "should not be in" the US.
Use of this term usually implies that an ideology is advocated or a challenge is being issued to find someone willing to state support for, or publicly do, the thing that no one is in favour of, or doing.