Bolt can be as biased as he wants on his private-funded tv show. However abc has an obligation to be unbiased due to government funded tv station.
As explained here, abc caught breaching guidelines.
http://m.smh.com.au/federal-politics/political-news/sarah-ferguson-interview-with-joe-hockey-breached-abc-bias-guidelines-review-20150217-13gbmj.html
& another
http://m.heraldsun.com.au/news/opinion/bias-against-tony-abbott-is-truly-sickening/story-fni0ffxg-1227224642841
"It is about an ABC that last week beat up Abbott for days for referring to a “holocaust of jobs” — he insulted Jews!, was the deceitful claim — yet didn’t complain when Labor’s Paul Keating referred to an “economic holocaust” and Greens senator Scott Ludlam to an “environmental holocaust”."