Ahh, but that's not the assumption.
When a person sees a (news) item on their Facebook/ETC. feed, they judge it based on the proximate source (the name/context of the person reposting it), not the ultimate source. There is a poll result making the rounds right now indicating that about half the time people don't even remember the ultimate source (they couldn't tell you if the video was mafe by NBC or The Onion), it really doesn't matter to them.
Stepping back a little bit...
People take their ideas from known and trusted people. At the same time their ideas affect who they trust, but the ideas are not the only factor. It is a complex system that is influenced, not 100% controlled, by self organization around ideas.
So if we use a 14 year old as our example, she has a network of people she trusts for reasons that range from sensible to outright bizarre. Maybe parents, likely teachers, certainly friends, commonly celebrities, apparently some politicians, ETC. The trust was formed for reasons that have nothing to do with ideas (a child doesn't trust her parents because they share similar views) but it influences views (a child who trusts her parents will likely share views with them). Of course the ideas she accepts will influence her choices, which affects the shape of her social network. If she accepts the idea that she shouldn't associate with people of a certain type, her social network won't have views of those people represented.
That's why environments like schools are so important to influencing ideas. They force proximity helping to create trust relationships that wouldn't otherwise exist (students trusting teachers, students from diverse backgrounds trusting each other, ETC.). Those can then be used to distribute ideas of all kinds.
The only way a company like NBC can be the proximate source (rather than creating supporting media to help others influence ideas) is if there was a mechanism to force proximity and therefore establish a trust relationship. For example if there were widely distributed devices that were limited to only presenting content from them, or maybe a handful of similar companies. An example would be the old television system from years ago. That would work for people who grew up in that environment but it isn't going to cover many 14 year olds today.
Well.... maybe we've been misunderstanding each other.
It seems, from what you wrote above, that youre talking about 'NBC' (generically speaking) being the proximate source influencing (or not) the 14 year old.
But thats not what I was talking about. Its the story that will have influence on the new generation (almost) regardless of which network is the 'breaking news' source.
Whether NBC, ABC, CNN, FOX, or even Facebook, is the proximate source doesnt really matter much to the 14 yr old from what Ive personally observed from my 9 nieces and nephews ranging from 10-18.
But all of them are also 'friends', on facebook for example, with the older cousins, aunts, uncles, parents etc (except me because I dont do facebook).
So while they all don't really watch TV news much, they do see their older 'friends/relatives' (their 'sphere of influence) sharing the story. Some are very conservative, some are pretty liberal, but not terribly so, to fairly neutral and we all live with about a 10 mile radius of each other.
All kids at some point start forming their own opinions on these sorts of things. Some follow their parents, some rebel against their parents etc. But they all see the story on their hand held devices being (this is an important piece) shared by various trusted liberal/conservative/neutral relatives so the news story must be important. (We're close and celebrate holidays and birthdays (and its a lot of birthdays), and summer bbq's together regularly and these topics do come up often)
They, the kids, click the story of 'ghost guns' to see, and judge, for themselves, And its story that demonizes the ability to make your own gun.
That will influence their young minds. Not because it came from NBC or Facebook but because kids do form their own opinions and do have a 'sphere of influence' that is diverse among their trusted relatives that they spend quality time with.
Out of your 75 million number, there has to be a couple million in similar situations; heck I just accounted for 9 young minds. I'm surely not that unique (and I didn't even count my out of state nephews). They will have been exposed to the difference of R's and D's in regards to guns, and they have seen/heard that story that demonizes guns in general and 80% scary home made ghost guns in particular.
That couple million votes can be the difference in the next election.