The song's criticism on mass media is mainly related to sensationalism.

"Good" things are usually not sensational. They do not demand attention, hence why the code of known/unknown based on selectors for attention filters it out.

Reference Hans-Georg Moeller's explanations of Luhmann's mass media theory based on functionally differentiated systems theory.

Can also compare to Simone Weil's thoughts on collectives and opinion; organizations (thus most part of mass media) should not be allowed to form opinions as this is an act of the intellect, only residing in the individual. Opinion of any form meant to spread lies or parts of the truth rather than the whole truth should be disallowed according to her because truth is a foundational, even the most sacred, need for the soul.

People must be protected against misinformation.

Very impressive observational skills used by Sherlock Holmes yet again, and points the suspicion back to Roylott, away from the gypsies and the handkerchief idea.

Holmes is not impressed by the idea her dying words "the speckled band" was a reference to the handkerchiefs, telling Helen to go on with her story even though he is not believing it. Based off of all of the other details he has focused on, the handkerchiefs have nothing to do with those and he has been able to deduce that this narrative is wrong but will hear it out because he wants the entire story in order to get more details that he can observe.

Sherlock Holmes focusing on a small detail of the story yet again, showing his observational skills and creating a potential narrative of his own of what occurred that night.

Holmes asks no questions about the death of her sister other than these two small details, again showing his incredible attention to detail and a way for Doyle to implement foreshadowing.

Another show of Sherlock Holmes picking up seemingly small details, that turn out to be large hints.

Another hint that Doyle is giving the reader through Sherlock's incredible observational skills. The whistling in the night does not seem to be very important on first glance, but Sherlock finds this detail intriguing and something that bothers him.

Gives the reader a hint that what Helen just told Holmes is important, shows that Sherlock is very adept in his observations and deduction skills in his detective work

The way I think of sensationalism today is newspapers that are online click bait titles such as Donald Trump starts a war with Russia for example is click bait and so is Rosanna Pansino comes up with a new cake recipe.