Teacher and Student (opposite sexes)

I've seen many cases where a femal teacher has a sexual relationship and is caught with a male student and many people (usually the men) would say things like
"It's a guys dream", "If she's hot than it's okay", and, "It's not wrong if they both want it"
Now this is different when it's a male teacher and a female student. 
There's the look of disgust and many people look at the man with rage and call him names such as a pedophile and monster. They pity the girl and fear for her, thinking the complete opposite of what would happen if it was reverse sexes.
How? And Why?