Maybe if we ignore it it’ll go away.

seen from Italy
seen from Nicaragua
seen from Germany

seen from United States
seen from China
seen from France

seen from United States

seen from United States
seen from United States
seen from China
seen from United States
seen from Japan
seen from Nepal
seen from Australia

seen from Netherlands
seen from Türkiye
seen from Saudi Arabia

seen from Germany

seen from Germany
seen from United Kingdom
Maybe if we ignore it it’ll go away.
The shapeshifter in 10.06 was presented as fairly sympathetic. Choices are a factor in whether to follow “monstrous” behavior or not but so is “nurture” and this girl was locked up and emotionally abused. She wasn’t showing insight or willingness to change, but she was already a victim before she died. The shocker in 10.06 wasn’t that Dean killed her, or about Dean himself being remorseless or wrong. The shocker was how he killed her, the unnecessary shots, the way the MoC was in the driver’s seat. It’s not as simple as it making Dean do stuff he wouldn’t maybe feel necessary, as it takes what’s there and takes control away from him, turns Dean into something he doesn’t want to be and even more, something that really isn’t who he is. Despite the violence of his life, the fact that he’s a soldier, he is not the “born killer” of the promos. We’ve seen who Dean really is at the very center.
The men Dean killed in 10.09 were a less complicated situation. Abusive, sex-traffickers, potential rapists whose target was a teen-age girl. They out numbered Dean. The shocker isn’t that Dean had to use violence against them, or that he wound up killing them (although not going downplay how it might make Dean feel to have to kill the humans among them—SPN has made a distinction between killing monsters as part of combat and the rare occasions when it’s necessary to kill a human). Again, as with the more complicated shapeshifter kill, it’s how it was done. The extremity of the violence and that Dean was not entirely in the driver’s seat when it happened.
There’s no judgment from Sam and Cas when they realize what happened. Fear for Dean, horrified at what happened. They’re frightened, but most of that fright is at losing Dean, what it’s doing to Dean.
However, the scary here is not that it happened in these specific contexts. It’s HOW. It’s the thing itching under Dean’s skin, and the nature of it and how frightening that degree of violence is. It’s like the MoC takes the “hunter” aspect and turns it into “monster/killer” and Dean can’t hold it off, it takes over.
But it’s not a case of, the shapeshifter kill is shocking, and the killing of the men in 10.09 is not. Different contexts and situations, still scary.