How will you explain to your children...

[pocaracas]

I am gay. The only breeding I do is with other men, and thankfully we cannot become pregnant.

So if homosexuality is genetic, why hasn't it been breed out of existence by now?

Up until the XX century, people were almost forced into matrimony and had to have children, regardless of the existence of any attraction between the two parents.
Homosexual tendencies already present in ancient Greece, have thus, remained around, however hidden.

These past few decades have seen the homosexual individuals released from such bondage and become somewhat accepted. From now on, homosexuality should decline for the exact reason you expect it to have been bred out.
However, I doubt it will ever go through a complete wipeout, exactly for the same reason many other genetic disorders still pop up on a few individuals...