It's very simple, There is very little, if anything written in the books of John Norman about gor that even mentioned gay in gor, it was not even mentioned when speaking about panther tribes and panther tribes are all woman or female tribes.
Therefore assumed that there were no gay or lesbians in gor.
In a society such as gorean, gay and lesbian would be considered extremely undesirable, it would deeply offend the honor of many warriors and free woman, therefore, must be destroyed to remove this stain on the honor on men and woman.
Also, you must remember, you cannot make anyone accept something they do not and will not accept, even in a virtual world.
In a male dominated society such as gor, gay and lesbians would find themselves very much unwelcome and unwanted,