Sydney - US rapper Macklemore vowed on Thursday to "go harder" when he plays his hit gay anthem at Australia's rugby league grand final, despite protests from "angry old white dudes" during a national vote on same-sex marriage.The musician is due to perform his song Same Love at the season-ending game in Sydney on Sunday, pitting Melbourne Storm against the North Queensland Cowboys.But this has riled some conservative politicians who are campaigning against legalising gay marriage, as up to 15 million Australians take part in a voluntary postal vote on the issue."I'm getting a lot of tweets from angry old white dudes in Australia. I think there is a petition today to ban me from playing," he told US radio.This, he said, had had only encouraged him to "go harder".Charged debateThe charged debate has seen many Australian sports organisations come out in support of the "yes" campaign, including the National Rugby League. Former Australian prime minister Tony Abbott, a leading voice on the "no" side, on Wednesday endorsed a petition calling on the league to withdraw its backing of same-sex marriage. "Footy fans shouldn't be subjected to a politicised grand final. Sport is sport!" Abbott tweeted.The petition, initiated this week by a former rugby league player Tony Wall, says it will be difficult to watch the final "with a LGBTIQ (Lesbian, Gay, Bisexual, Transgender, Intersex & Queer) anthem taking centre stage".It has so far attracted nearly 10 000 supporters.Attorney General George Brandis said it was "bizarre" that Abbott would target Macklemore. "This particular song is one of four songs I believe that Macklemore is singing, it's one of his most popular songs, and for Mr Abbott or anyone else to say that it should be banned I think is a bizarre thing to say," he said.Results of the controversial ballot are due in mid-November.