Relax Circa. It is not personal.
TL;DR
1 - The "Six Corporations" claim comes from a viral meme in 2011 originating from a (now-defunct?) blog about "Insights on Family, Career and Money" and mostly about financial planning for college (frugaldad.com).
2 - It was not true then; it is less true now (more media corporations now).
3 - Other industries are far more concentrated than media; so what?
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Frugaldad.com was a personal blog about personal finance. It is apparently gone now.
In 2012 Business Insider published an info-graphic from the blog, with some criticism, but no analysis. And the Wikipedia page (I think that is where your quote is from?), is really questionable (lots of requests for substantiation).
Apparently, FrugalDad´s source was a 2004 book, The New Media Monopoly by Ben Bagdikian, a well-known left-wing journalist biased against large corporations. The book has no source or footnote given for his claim of media control.
The supposed "Six" from over a decade ago has grown with the emergence or expansion of other corporations (e.g. Alphabet, Amazon, Microsoft, Reuters, Bloomberg, iHeartMedia, Twitter, Facebook, etc).
HOWEVER, there is concentrated control over about 50% of United States media by under a dozen corporations and 15 billionaires (that is from my own wasted time educating myself on this).
So you have that going for you.
And anyway, so what?
There is less concentrated control in half the media than there is in the nearly full-market control by fewer corporations in:
Aircraft– four companies dominate almost all airliner manufacturing (Boeing, Airbus, Embraer and Bombardier).
Cars- almost 80% of the market is controlled by 6 companies (GM, Ford, Chrysler Group, Toyota, Nissan and Honda)
Cell Phones- Just two operating systems (iOS and Android) make up over 90% of the market. And five manufacturers make up more than 90% of the world market (Samsung, Huawei, Apple, Xiaomi, BBK Electronics).
Beer- two companies (Anheuser-Busch InBev and MillerCoors) make up 75% of the US market, everybody else is under 2%.
So what?
Do not let some left-wing conspiracy theory mess with ya´ Circa! Relax.