It is
not true that all gun owners already do some sort of training. My state, SD, is an example. We do not require a permit to buy any firearm. We do not require a permit to carry in your home or place of business. We do not require a permit to carry openly in public.
We only require a permit to carry
concealed. No class of any kind is required to obtain this permit. $10 and a simple application to the Sheriff's office will get you a permit in the mail within 2 weeks, provided you pass the background check.
Further, we are moving away from requiring a permit at all, to carry concealed or otherwise (
link). Permits will still be available so that citizens may take advantage or reciprocity laws with other states.
We view the right to carry a firearm anywhere in public as fundamental a right as religion and speech.
However, we also honor the concern over untrained persons carrying a lethal weapon. Our compromise, therefore, is to add basic gun safety as part of the mandatory highschool curriculum; a class taught by law local enforcement which would cover law, maintenance and basic marksmanship, to include range qualification.
The end result would be a trained citizen lawfully enjoying their right to carry without be infringed upon by permit requirements. Both sides of the issue would get everything they want.