There's a lot of evidence for respiratory transmission.
Given that the current outbreak has largely been linked to sexual activity among MSM, the doctors carefully ruled out the possibility of sexual abuse, thoroughly documenting the boy's history and testing him for a slew of other sexually transmitted infections, which consistently came up negative. The boy also did not have monkeypox lesions in his genital area, which has frequently been seen among infected people in the MSM community.
The doctors' best—but concerning—guess as to how the boy became infected is via respiratory transmission.
There's also a study I posted that's on the front page right now. A hospital in the UK found the virus in the air 6 feet above the patient. So it's not just droplets, it seems to be airborne.
I guess people aren't willing to accept this yet.