These discussions always degenerate, as they are accross a cultural divide so wide often it's hard to understand what the people on the other side are saying.
In England, as with the most of Western Europe, murder rates are low, there is no death penalty, private gun ownership is almost impossible (to put it into perspective 0.007% of crime in the UK involves a gun) , we have reasonable personal freedoms, we haven't any fear of the government shooting us down in the streets or cancelling elections, there are very few 'no-go areas' even in the largest cities, and we haven't been properly invaded for 937 years.
Now, if you grow up in the States, you have a high murder rate, you have the death penalty, private gun ownership is comparatively easy, you have reasonable personal freedoms, you've had unarmed students shot in the streets by soldiers within the past thirty years, the last election would have been declared null and void if the UN had been monitoring it, most major cities have 'no-go' areas, and you've had your Capital City burnt by invaders in the past two hundred years.
Thus, to an American it can seem obvious that if you got rid of the death penalty, murder rates would rise, that you need guns, as there are too many in public circulation to ever control (and if you DID try to collect them door-to-door with the US Army, then the NRA would come from joy, shouting 'I told you so!'), you cannot trust your government, poor areas of your cities resemble war zones, and you never know when those damn Brits will try something again.
Some of those opinions are quite reasonable; in the US, the horse has bolted and bred, and there never was a stable door in the first place. Rather than try to control guns, it would probably be better if you make them compulsory. That way at least it would be fair. But the fact the entirity of Eastern Europe overthrew totalitarian government WITHOUT GUNS makes the 'we need it in case the government are nasty' argument is a crock, as is the death penalty detering violent crime. Please don't mention the Ammendment to the COstitution that allows you to bear arms. It is an Ammendment, i.e. a change. Just as Ammendments relating to sexualy and racial equality were introduced as society changed, so it is equally possible that some Ammendments have a sell-by date. In the UK, as we have few guns and few gun problems the logic is obvious, to us, and judicial killings are just barbaric, as it impossible to avoid killing innocent people in a judicial process that includes execution, and it doesn't really put people off commiting crimes anyway.
Thus, culturally, it's quite possible to disagree with someone in this arguement and for you both to be equally right, as we are moralising on another culture, and morals don't always work when you use one culture morals to analise anothers.
One of the chief factor relating to gun violence is, rather obviously, drugs. You cannot eliminate drugs, but you can eliminate the mechanisms that make drug users use violence to get hold of money, or to control the supply of drugs, or to compete with other suppliers. However, it is far more acceptable to the average person to put up with the diet of drive-by shootings on the news than it is to consider decriminalising drugs, as, despite evidence to the contrary, making drugs legally available at fair prices is too damn scarey as people mistakenly think it would make things worse.