In this context, the violent nature of the group is reasonably indicated by the actual incidence of violent crime, not by the power of the weapons (or fists) that are used.

Group X (say 5000 people) has 500 violent crimes. Since they can't use guns, they use things like knives, fists, rocks, etc.

Group Y (say 5000 people) has 400 violent crimes, 50 of them involving guns.

Of the two groups, which contains the higher proportion of violent individuals?

The British claim was that Americans, by nature or nurture, are *as a group* far more violent than the British. There's no way even to guess whether one group or the other, with equal access to guns, would be more likely to use them.

For all we know, if Group X had had guns, they'd have used them far more often than did Group Y. But we don't know and can't speculate. All we *do* know is that Group X has a higher *rate* of violent crime, and by that measure is the more violent group.

Whether the "average" member of Group X is more or less violent than the "average" member of Group Y (i.e., more likely to use a gun if one is available) can't be determined from the evidence.