The media want views - they want clickbait. And the easiest way to get clickbait is to report on something controversial. The media don't particularly want controversial, they just want something that gets views and can attract more money from advertising. And that is Trump calling mexicans rapists.

All of those things are also true for SuperPACs and other forms of political speech by private citizens.

Actually no. (And stop calling corporations private citizens - they are actually body corporates). Do you think SuperPACs advertise on Fox or CNN to get votes? - they only do to get the core out to vote (or support their candidate in the primaries), but they are not seeking to change their minds, because its independents who decide the elections, and they consume multiple media forms much higher than party supporters - "Various independent respondents cited eight sources other than the two major television networks" compared to party supporters.

And why? In the 2014 midterms, 92% of Democrats voted for their own party and only 7% voted Republican. In the same election, 94% of Republicans voted Republican while only 5% voted Democratic. So the only people who will change their vote is independents and Superpacs target those voters, having to use a variety of media (billboards, internet, newpaper and TV (the less bias channels)). As you can see this is what makes Superpacs powerful - their ability to target independents.

Now 30 years ago this is what happened: Corporations might want a particular candidate to change their policies. They give that candidate money. This is Disclosed. Suddenly journalists see the records of this money and start asking the candidate questions about it, now if its with 60 days big corporates/TU's could not defend the candidate. Rather the candidate alone had to defend their policies to the electorate. The big corporations or trade unions (or super-pacs) could not jam up the media full of BS (lies) or try and divert attention away from these policies. Rather they had to sit there and endure it - they knew they would be exposed. This actually created a culture where big corporations were reluctant to give money because of how it would be seen.

These days there is no exposure, so no one gives a shit. Now it becomes about attacking the player not the policy (Run attack ads saying: "did you know Republican X voted AGAINST the 2nd Amendment" - when actually it was for high volume magazine clips), actually you can say anything - even if it BS, it won't be exposed as a lie (until after the election), even create disinformation campaigns, etc. Now I am not saying this did not happen before - it did. But it was at a much lower intensity as it was funded by a political party not a guy trying to get a pipeline approved. And there lies the difference - A Political Party trying to win a seat (for a majority) vs a donor trying to get the guy to win a seat to support his own individual issues.

And yet Comcast can feature a candidate at length on one of its women's programs, or on its boomer comedy programs, etc. at any point during the cycle. Let's say a 30-second commercial on a Comcast program is worth $250,000. What do you think several minutes of free product placement on that show is worth?

I am not sure about the media in the US, but as part of TV licence requirements in other countries there is mandated equal time for both political parties over a certain time period (usually 30 days - which is when most independents actually decide). As for free product placement - well if your the presidential republican candidate on fox news - not much - those people are already going to vote for you. And as for money - you example is incorrect. $250,000 is for metro, prime time markets (think NY, LA). And usually with prime time spots you get bonus spots (1 Prime time : 3-5 non prime spots), so most of the time the $250,000 is actually worth much more than $250,000, it might get you $1M+ worth of exposure. And with a couple of million spent on a regional network (nobody pays $250k a spot for regional media), you could actually dominate a market.

So, back to the core question: the billionaire family that runs Comcast has formed corporations that broadcast its point of view on political candidates and issues to millions of Americans, anytime it wants. Why do you think that other citizens should be blocked from doing the same?

Actually it is NOT the core question - the core question is - can non disclosed super pac money influence political candidates more than any traditional media? Yes. And thats why the Koch brothers have not bought TV stations - because a TV channel can really only support a party (and even then their are limits - they don't want to go to far if it alienates one of their big advertisers) - and they might get no traction on a particular issue that the owner has (see Murdoch with BSkyB). As an example in Australia we have a radio station called 2GB which is pro conservative. Now the conservative PM doesn't even bother to go on to that network - because the party already has their support - he does not need to go on. And yet if the conservative media was so powerful then he wouldn't of even been PM: http://www.theguardian.com/media/2015/sep/15/a-painful-morning-for-alan-jones-who-told-malcolm-turnbull-hed-never-be-pm

so the idea is that media is less powerful because they are preaching to the converted. Superpac's power comes in from getting the support of independents - something that biased media has a lot of trouble dong. As such superpacs can be more powerful than Fox to a political candidate. Also because of the ability to hide donations Superpacs can influence candidates more on particular issues than the media can.