Wow, props for the well addressed, calm response. It deserves a reply.
There were a number of areas I didn't make reference to purely for the sake of being brief, but I'll raise them now.
I did consider the issue of sports, however that can easily be tidied up with tighter restrictions on equipment. As is the case in many (most?) other countries, the equipment isn't owned by individuals, but "leased" from the ranges. Ammo is counted in & out, so it can't go "missing".
As for your burglary comment, I again point out that in an unarmed state it's highly unlikely that the intruder would have a gun themselves. This would be due to a) lack of availability & b) being caught in possession of a firearm can turn a 6 month sentence into a 40 year sentence.
I can possibly empathise with people not wanting to give up their arms once they've already got them. a) for sentimentality, b) because the non law abiding citizens who have now got hold of guns, won't mind breaking the law to keep them. This leaves the law abiding citizens at a distinct disadvantage.
This isn't an argument *not* to disarm the populace, just that it would need to be done carefully.
You can probably draw a very similar analogy with nuclear proliferation & MAD - no one wants to make themselves vulnerable by backing down first, but everyone agrees it's a counter-productive situation that needs to be resolved. In fact it's almost exactly like MAD, except with nations instead of individuals.
Now don't get me wrong, I'm a fully fledged, card holding civil libertarian & I'm not averse to arguing controversially strong views in support of our civil rights. However, I don't think every man, woman & child should have the natural right to possess equipment whose sole design & purpose is to kill other people.
I the same light, I also don't have problems with the government restricting the public's access to lethal chemicals & radioactive compounds (which have legitimate scientific use).
Proceeding onto the research & article...
Bad data. They are only accounting for people *IN* Philadelphia, PA. They aren't comparing gender, age, upbringing, income, ethnicity, or other factors *from other areas of the country/state/world*.
Unless the PA is a total anomaly which bears no similarities to other states, I think it's fair to draw inferences - and 667 cases isn't a bad sample size. At no point did the study overstate the certainty of its conclusions.
As for the other factors you mention, are they relevant? The aim of the study was simple: Will being armed make you safer?
Yes, there are still gun related crimes in the UK, that's unavoidable. However, incidents tend to be limited to the rare gang shootings on a couple of infamous council estates. Armed crimes (lethal or not) outside of this tiny subset are infrequent enough that it'll be covered in the national news for days.
The Duggan case you refer to was a good example of this. The alleged gang member was in mere possession of a gun, having only just received it & the police were all over him.
Our homicide by firearm rate is 0.1/100,000 (40/yr). Taking into account that most incidents are within the small communities mentioned above, I think that shines quite well on us as a whole.
As to your last point - the fact people have died in gun fights isn't an argument for more guns.