Don't say a word.
its my personal opinion that young adults almost completely lack the ability for serious analytical thinking. Much as they want the world to beleive they are "their own person" they generally regurgitate the "logic' that the most impressive person in their life has fed them.
And lest anyone think I am bashing others, being 35 myself, I happen to believe the real ability to think critically [b]begins[/b] mid to late thirties. True. [BD]
So, in answer to your question....given young peoples handicap in logically working things out, you want to capitalize on their ability to "learn truth" tactilly, thru touch and personal experience.
Take them to the range. Under careful supervision, show them the workings of the .22 LR rimfire rifle. Stress safety, but don't bore them with techy data and the things you and I drool over, cuz it will bore them. Have them fire the rufle themselves. Use "knock down" type targets, that are reactive, where they can "experience" the fun of shooting. Generally punchin paper, that'll make you and me giddy, will bore them.
[b]Summarizing, when they come to regard shooting as fun, THEN they will regard it as morally right. But they'll have to EXPERIENCE it for themselves. Book lurnin' will NEVER do.[/b]
THEN, [b]SLOWLY [/b] begin indoctrinating them with the logical truths re: gun wnership and the second amendment.
Much as we like to bash teens morals, they STILL operate under a very strict, albeit divergent, code of morality. its their nature to do so. Only in later adult life do we learn to violate our own code of morality.
When they regard shooting as fun, they will regard shooting as right. when they regard it as right, THEN they will be willing to learn and accept the truths of Second Amendment gun ownership.
Good luck.
[edited to add]
By "analytical / critical thinking" I mean the ability to evaluate your own long- held beliefs, those beliefs which were fed you by that "most impressive person" and abandon those cherished beleifs in the light of evidence to the contrary.