10 Dumb Decisions In Doctor Who We Can't Forget
3. Massacring The Silence - Day Of The Moon
It does bear remembering that the eccentric main character of this show that was originally intended for children has canonically committed genocide both on and off screen. The Sixth Doctor was charged by his own people in The Trial of a Timelord with wiping out the Vervoids, the Seventh Doctor destroyed Skaro in Remembrance of the Daleks without much hesitation - and that's just the classic series.
There have been a few instances of this too in the new series, but none as oddly flippant as the Eleventh Doctor's actions against the Silence in Day of the Moon. The alien race had the ability to edit themselves out of a person's memory, making you forget all about them the second you looked away.
They had been on Earth for centuries and were manipulating humanity into doing terrible things. The Doctor's solution to this was to use a recording of a Silent saying that humans "should kill us all on sight" in order to turn everyone on Earth into an unwilling murderer.
Not only does the Doctor wipe out a species, he makes humanity complicit in it. There must have been a better way than this.