what programme you're talking about, or the context in which the references to homosexuals was made. That makes it difficult to comment in much detail, but in general terms I find it astonishing that you should be so outraged, simply because your four-year-old knows that there are homosexuals in the world.
You talk as if some horrible, irreversible psychological damage will occur as a result, but of course it won't unless you make a big thing of it. Children should grow up knowing about these things, and knowing about them in a relaxed and open fashion, rather than having their ears and eyes covered at the mere mention of homosexuality. Better to have a suitably simplified explanation from your own father, rather than pick up a playground version from another child.
Is being gay really so acceptable now?
I'm frankly astonished that you ask - of course it's acceptable, why should it be otherwise? What would your attitude be if your daughter told you she was gay herself in the years to come?