Is a knee jerk reaction to call an internet picture a fake about as bad as blindly believing a ridiculous picture is real?

I posted this picture that I came across, and one of my acquaintances immediately pronounced it as “fake.” She wasn’t able to explain why she thinks it’s fake, except that there are a lot of fake pictures floating around out there.
It’s not really important, but I just found it odd. It’s like the back side of believing everything you read and see is REAL.