john and stipe issued a joint statement calling for equal rights of transgender inmates .
` transgender women in male prisons have an equal right to protection from violence and abuse in prison , and yet they continue to face horrific injustices , ' statement read in part .
southern poverty law center in february filed sued georgia department of corrections on behalf of ashley diamond , a transgender woman .
diamond , 36 , identifies as a woman and has been taking hormones since age 17 .
claims lack of medical attention has harmed her transition process .