Wrong analogy. This was not an error. These men KNOW they are committing a crime.
If you give someone a car and say “This car is stolen. If you drive it, you could be arrested”, that would be a closer analogy.
Let's be clear. The crime was "thinking" that the person was a minor. They did not KNOW, nor could they KNOW, how old the person was.
Ironically, if a 13-year-old went on an adults-only chat room and posed as a 20-year-old, no adult would be arrested. Where an actual child IS harmed, everyone looks away.