The question is valid.
Did they have a right to defend themselves?

Yes , obviously.
Every animal possesses the right of self defence, that's why we don't blame a cornered kangaroo or a koala bear for ripping the living excreta out of anyone that attacks them.
The same rights extend to humans and what's more is recognised by our Australian courts of law.

There is nothing vague about the right to self defence.
What is vague is the thinking of those who would deny the right.

As I've said earlier - of course there's a right to self defence. Great. We're agreed. Everybody has the right to defend themselves.

Nobody would argue otherwise because it's so obvious.
So unless you'd also like to point out that you have the right to eat, the right to speak your mind and the right to ride a bicycle, it's quite clear that you equate that right as the right to own a gun. If I'm wrong on this point, feel free to clarify.

The right to defend yourself doesn't equate to gun ownership. It's a separate issue. Efforts at gun control are not an effort to rob you of your right to self defence.

By the same logic, I have the right to eat what I wish do I not?
Then why don't I have the right to buy half a kilo of heroin?

Largely because were everyone to have the right to buy heroin, there would of course, be more heroin produced. It is not my right to buy heroin, because of the detrimental effect it has on society in general. A functioning society is why some rights are curbed by law.

Of course, I also have the right to object strenuously to efforts at reducing gun control. Rights are wonderful things ain't they?

TRTL: Thanks for clearing up that misunderstanding.

I'm personally quite ambivalent about gun ownership in Australia (and I don't think I'd own one even if I could), and indeed, things like the legalisation of drugs. In principle, I'm for them (in that I think if someone is minding his own business, then why not?), though I don't know what the unintended consequences would be, and I think Australia functions fairly well as it is already. However, I'd err on the side of punishing those who can't have or use these things responsibly, rather than on a blanket policy.

Having said that, I don't know that the example of heroin is necessarily a good one since the "War on Drugs" has not been that successful on a world scale. It's certainly created more criminals, both in terms of users, and also in terms of dealers (compare the behaviour of both to say, someone buying or selling cigarettes, alcohol, pharmaceuticals, or even non-drug products), and it costs taxpayers a lot of money to maintain this war. I think there are much bigger fish to fry in our society than heroin.

Of course the right to self defence doesn't equate to gun ownership.

But if one is attacked by someone with a gun then a gun is the only practical means of defence.
If one is attacked by someone with a hatchet, machete or an axe then a gun is mighty handy, but, if up to it physically, then an axe or a machete would do the job; messy but possible.

Now the law doesn't say that you cant keep an axe etc. but it does say that you can't keep a gun handy.

The State having removed/forbidden the means of defence ought to assume the mantle of protector.

It hasn't, cannot and will not. The police service does not exist for the protection of the citizen. It's not their job.

So whose job is it? When there is a home invasion how can the home owner protect the family?
As you say, there is no argument about his/her right to self protection, the argument is about having the means.