Do you, perhaps, have statistics on the number of violent criminals who belong to gun clubs? I'd be willing to bet it is very low.
The law isn't that bothered about conventional violent criminals from joining-because they can't anyway.There are always strict police checks and cops themselves are members of gun clubs anyway.
The law is concerned about fantasists,violent,psychotic neo-Nazi supporters,KKK sympathisers(David Copeland),Rambo wannabes and survivalist fanatics and finally socially-inadequate individuals-who might,just might,slip the net by joining up-then they are free to acquire licenses and variations legally.
There is no criminal or mental history,in those checks-for those types of individuals-who wish to own weapons-because they have never commited a crime before-so no criminal record.In the case of Micheal Ryan and Thomas Hamilton,it was a down to Police incompetance-more so than anything else-but the authorities created stricter legislation,to prevent those psychos-who hold and held licenses and who don't draw any attention to themselves-from trying to kill or create havoc,with their weapons.
The argument for stricter controls on firearms is:"A Firearms license,is only a few bits of paper,with police checks and will do nothing to stop a person committing mass-murder,with their guns-if suddenly they become angry or mentally-ill.
Most crooks worth their dime,wouldn't commit mass-murders on civillians-but those types of loonies,that I have listed above-might do.This is why there are bans in the UK.The fear of the next Hungerford or Dunblane type of murderer,that would be commited by a license-holder is too much to bear in the UK.
Those traditional crooks look upon mass-murderers with a level of contempt,that is unbearable and would do some serious damage to them-if they got half a chance to-in the first place.