Yes, Macklemore came out with "Same Love" which voiced his stance, and support, of same-sex marriage. The track, which was inspired by his two gay uncles and godfather, has brought a lot of attention to the Seattle rapper, especially based on hip-hop's history of homophobia. But he's not technically the first rapper whose rhymes are accepting. In fact, Chicago rapper Common has a history of employing homophobic lyrics like, "In a circle of faggots, your name is mentioned..." on his track "Dooinit" from 2000. Two years later, he would change his view and attitude on "Between Me, You & Liberation" off and in future years, would regret his earlier lyrics after his fans reached out to him. On the third verse of "Between Me, You & Liberation" he rhymes about a man questioning his sexuality and the need to accept him.
If you think Macklemore is the first rapper to talk about gay rights then you should listen to: Common "Between Me, You & Liberation"