I have been addressing it.
I have addressed it several times, in several different ways.
You're talking about probability of an event, not the necessity of a weapon.
Whatver level of probability you might care to assign to a situation were you "need" a firearm to protect yourself doesnt in any way negate the fact that the most effective firearm for such situations is an atuomatic weapon.
You've already coceeded that you - the generic, civilian you - might "need" a handgun or a shotgun for prtection, therefore conceeding that there is some real, legitimate probability of same. Having admitted that, you cannot logically get past the point that, since if you "need" a gun, you "need" the most effective gun you can get, there is a "need" for automatic weapons.
At last, something to work with.
On probability. Yes I am referring to probability, that's so. If there was a very high probability of the average citizen (in Whereverland) being attacked by people armed with fully automatic weapons I would say that there's a need for someone to be armed with a fully automatic weapon in response. In other words there would be a need.
Now in not-Whereverland, a society that is functional, unlike my fictional Whereverland, the need is limited to the military and certain police units because the probability of attack by people with full autos is higher for the military than a civilian, hence greater need (I'll leave the CT police out of this to save time, effort and space but will bring them up if challenged on it).
In the US, is your society resembling Whereverland yet? If it ever does, then I would agree, there would be a need for full autos.
In my country, which is my frame of reference of course, it's nowhere near Whereverland, hence no need for full autos by civilians.
Your second point. In public policy terms it's not a good idea to have all civilians able to get legal access to full autos. Not only is there no need (absent the Whereverland scenario), it's undesirable.
As for your argument that you need a full auto because you need a handgun - I'm sorry, I just can't take that seriously because there's no logic to it. Using your rationale I could defend hand grenades for individuals, you're just extrapolating to a point which is convenient for you but which doesn't bear up under examination. So, let me ask you a question. In your extrapolation from handgun to full auto, do you consider that you can go past full auto to much more powerful weapons. I think bazookas have been mentioned. But let's go further. Why not tactical nuclear weapons? If so, why? If not, why not?