It is highly unlikely that, now or ever, any woman would wish to abort a foetus that showed genetic signs of basketball incompetence - few poor ball-players are the focus of social malice and abuse.
Some homosexuals, however, are subject to such malice and abuse (sometimes from their mothers and their fathers). There is therefore a stronger likelihood of suspected homosexuals being aborted.
To allow the reinforcement of this likelihood would appear to condone the "stamping out" of homosexuality. It should not be surprising that homosexuals take offence at such a notion.