How Does Same Sex Eroticism Fall Short??

It's Sexual SELFISHNESS  -  
A general love of the self is normal, and erotic self love is really quite common.  
But we are taught from childhood that selfishness (beyond a certain point) is bad.  
A robust concern for OTHERS is part of what's called "the social contract."  
And since same-sex erotic love focuses on the same (type of) organ  
that you yourself have, it (same-sex eroticism) is considered self centric,  
selfishness epitomized  -  sexual narcissism,even.
  
Likewise, because the opposite sex (the genitalia thereof) is NOT a copy  
of that of the self, heterosexuality is deemed less self-centered,  
and therefore more pro-social (in line with the social contract).  
Plus heterosexuality lends itself to altruism (concern for others).  
Does that make sense?
  
Diversity suggests differences, as opposed to drab sameness.
Heterosexuality, by definition, involves differences, variety.
So it is synonymous with diversity, more so than homosexuality is.
Tell me if i'm wrong - in your humble opinion.

PS: Altruism, what is it?
To live for society, as though it were a marriage partner.
"Hands across the ocean," to dream of all mankind living as one,
The triumph of internationalism over crass nationalism !!
Finally, the friendship of a nation with the nation farthest away,
The ones most different from us, even the most alien.
Think of that as a great macrocosm.
But what is the microcosm that captures the essence of that great macocosmic hope?
It is a common, everyday relationship involving polar opposites: a man and a woman,
Namely HETEROSEXUAL MARRIAGE, "the reconciliation of opposites," as philosophers put it.