Angry fans of Australian musician and vaunted vegetarian Xavier Rudd want to know why the animal rights activist has allowed one of his songs to feature in a new KFC advertisement.

Rudd's hit song Let Me Be is the backing track for the fast-food chicken chain's new video ad promoting the 'Home Cricket Ground' range.

The tacit support for the factory-farmed chicken giant has perplexed Rudd fans, whose long standing animal rights advocacy saw him voted Australia's Sexiest Vegetarian by PETA in 2008.

The musician's Facebook page and Instagram posts have been hijacked by users venting their frustrations in comments ranging in sentiment from confusion to outrage.