Onus would be on Izzy. Not an employment lawyer but i think it falls under the Fair Work Act:
351 Discrimination
(1) An employer must not take adverse action against a person who is an employee, or prospective employee, of the employer because of the person’s race, colour, sex, sexual orientation, age, physical or mental disability, marital status, family or carer’s responsibilities, pregnancy, religion, political opinion, national extraction or social origin.
Note: This subsection is a civil remedy provision (see Part 4‑1).
(2) However, subsection (1) does not apply to action that is:
(a) not unlawful under any anti‑discrimination law in force in the place where the action is taken; or
(b) taken because of the inherent requirements of the particular position concerned; or
(c) if the action is taken against a staff member of an institution conducted in accordance with the doctrines, tenets, beliefs or teachings of a particular religion or creed—taken:
(i) in good faith; and
(ii) to avoid injury to the religious susceptibilities of adherents of that religion or creed.
385 What is an unfair dismissal
A person has been unfairly dismissed if the FWC is satisfied that:
(a) the person has been dismissed; and
(b) the dismissal was harsh, unjust or unreasonable; and
(c) the dismissal was not consistent with the Small Business Fair Dismissal Code; and
(d) the dismissal was not a case of genuine redundancy.
Fair bit of discretion there. Izzy's lawyers would have to convince whoever is hearing the matter than his dismissal satisfies those points. Im sure there's oodles of case law about this.
The NSW anti-discrimination legislation doesn't mention religious discrimination in the workplace, mostly focusing on racial vilification.
There is no religious discrimination act, state or commonwealth. Interesting extract from commentary on discrimination act:
The Anti-Discrimination Act 1977 in New South Wales
Discrimination purely on the basis of religion is explicitly not prohibited by the Anti- Discrimination Act 1977 (NSW) ('the ADA'). Instead, complainants must formulate their complaints on the basis of race discrimination.
The ADA makes it unlawful to discriminate against another person on the basis of race. The word 'race', under the Act, is defined to include 'colour, nationality, descent and ethnic, ethno-religious or national origin'.
As a result, those who complain that they have been discriminated against on the basis of religion, must establish that their ethnicity coincides or is strongly associated with their religion.
He could argue that being Christian is intimately linked with being an Islander and this therefore constitutes racial discrimination.