This episode also too a big yellow hilight marker to a creepy subtext that is important to the show. One that is often referred to in passing in the show.
At some level there is anti-story contradicting the main story. In the anti-story, Sam and Dean are serial killers, destroying innocent people they mistake for monsters. (They also desecrate graves for no reason.) In this sub-text either the hunter subculture really exists as a homicidal delusional cult, or much of their interaction with other hunters is imagined.
This subtext is not the "real" story. It would be a strained reading to see the supernatural in this show as anything but real (within the story universe). Not just a radical reading of the text, but to explain away Bobby and Ellen and Jo and so on would requiring a reading that tied itself in knots.
But where this subtext is important is as contrast to the main story, a reading that is ultimately rejected, but keeps presenting itself for consideration. Like Jalepeno jelly. The jalapeno adds bite but really it is still a sweet jelly not a salsa.
It comes up all the time. The FBI had them listed directly as this type of serial killer. Bella at one point said they were the next thing to serial killers. Lots of other references to this through the seasons. Again, not that the either authorial intent or the way we read is that they ARE serial killers. But the show constantly wants us to seriously consider that for a moment before rejecting it. Raising and rejecting it gives a darker tone than not considering it at all.
I do wonder if someone has written fan fic on that premise. No supernatural elements. Sam & Dean are serial killers in our world with delusions.