What in the heck is "Socially Acceptable"?

In a world of people constantly shoving their cultural, religious, personal and social beliefs down our throats, I gotta ask.

What in the heck is "Socially Acceptable"?

Apparently it's showing standards of behaviour that are socially and morally acceptable, atleast that was one of the meanings I got when I googled it.

But to whom is it acceptable?  Who exactly dictates such standards?  

And what gives them the right?  Especially in this culturally eclectic society that we reside in.  

We as humans are constantly shoving our own personal beliefs down each others throats with the expectations that those to whom we teach, should be basking in the brightness of our sheer genius; when in turn we don't even take the time to listen or try and learn about those around us.

To be honest, the whole term "Socially Acceptable" kind of peeves me.  

In my opinion, it sets a vague standard and excuses deliberate ignorance in the sense that people will use it as a reason to push their own morals and beliefs on others, without consideration of the morals and beliefs of those they are trying to teach.

Sounds like "Socially Acceptable" is fast becoming "Socially become what we want you to be".  How is that acceptable?

How do we as a society become so disillusioned, that our reality becomes so entrenched in believing that everyone must follow in what we believe to be true when in turn, we don't give thought to what the other has to offer?

We are selfish.

Selfishness is often veiled with good intentions and if we're not willing to learn off those around us and accept people for their beliefs and who they are.  How can we expect to try and change the world for the better when we're not willing to accept the better from the world we live in.