Foreign nationals who are convicted of a serious crime can be deported, however, if a person is born in Australia and has an Australian parent then they are a citizen by birth, and do not need to apply for citizenship. Persons who acquire citizenship by virtue of being born in Australia with an Australian parent cannot generally have their citizenship revoked, so on the face of it, I do not believe your son should be deported.
The revokation power in respect of a criminal offence is here:
but it does not apply to persons who are Australian Citizens by virtue of birth:
However, the minister for immigration has signfiicant powers and the law is somewhat complex on as the Act has been revised numerous times, so it is possible there is some important factor in your son's history that is not clear from the limited information you have provided and if action is undertaken to deport your son you should seek the advice of an immigration lawyer ASAP.
Good luck and PLEASE RATE MY ANSWER.