Please do not create rules that would allow discrimination against adopting parents. To do so would permit biases to overrule best interest of the child/children. 

No loving adult would pry into - and make judgement on - the sex lives of would-be parents.  If the state wants to meddle, it should consider spending more time on background checks in order to rule out adopting adults who have a history of domestic violence or are listed as sex offenders.