The legislation contains an exemption if you have a ‘reasonable excuse’, and it lists some examples without restricting it to those. So I think the judge has fairly wide latitude.

Legislation: https://www.parliament.nsw.gov.au/bills/Pages/bill-details.aspx?pk=3987

93ZA Offence of displaying Nazi symbols

(1) A person who knowingly displays, by public act and without reasonable excuse, a Nazi symbol commits an offence. Maximum penalty—

(a) for an individual—100 penalty units or imprisonment for 12 months, or both, or

(b) for a corporation—500 penalty units.

(2) For subsection (1), the display of a swastika in connection with Buddhism, Hinduism or Jainism does not constitute the display of a Nazi symbol.

(3) Also, without limiting subsection (1), a reasonable excuse includes the display of a Nazi symbol done reasonably and in good faith—

(a) for an academic, artistic or educational purpose, or

(b) for another purpose in the public interest.

(4) In this section— public act has the same meaning as in section 93Z.