Personally, I'll be the naysayer here that everyone wants: They were shown pictures, and answered questions based entirely on pictures. Most of them still said they'd give the pen and say no to 'modeling' no matter how attractive the man was. Their inner personal opinon changed.
I think the study is flawed because interaction, body language, vocal tone, etc all can factor in. I've been creeped out by hot guys before.
Yeah, based on how the study works I'd imagine the subjects are just imagining that the more attractive photo is more charismatic person because that's how we're trained to think. If the attractive person sufficiently lacked in tact, I think they'd be significantly more likely to be insulted or creeped out. Likewise, if the unattractive guy was sufficiently charismatic, they'd probably be less likely to be creeped out by him.
Charisma is the real defining factor as to whether anyone is unsettled by another person. People are just trained to believe that attractive people will be more charismatic. That bias helps the attractive person in the first encounter, true, but if you don't know how to capitalize on that advantage, it won't make a difference. The inner creep will shine through. The subject's perceptiveness will also be a factor. If your subject is an idiot, then appearance is going to account for a much larger difference in how they perceive others than someone more observant and thoughtful.
I don't think it's a night and day difference. One of the biggest problems traditionally unattractive people tend to have is that they have a tendency to internalize the belief that they're unattractive and that reads in their behavior. People who do this behave in self-defeating and subtlety hostile ways that causes the subject to be suspicious of their intentions. That's just doubling down on your disadvantages.
As an aside, having an opportunity to even enter into an encounter with other people is harmed significantly by having resting bitch face. I speak from experience on that front. When approached, I'm a very warm and friendly person and I have several times been told I'm a very attractive person, but people do not want to talk to me. I don't have to say or do anything overtly. First day of a new class in college, you could see a ring of seats left empty around wherever I sat on any given day. I've been told I give off a "spooky" or "haunting" vibe. Someone described it colorfully once as "An aura of 'go the fuck away'."
My point being, there's lots of factors that go into reception. Attractiveness is one, but not even close to being the whole thing.