As long as we're talking about the difference between orgasm and
ejaculation, let's get to an extremely pervasive myth:
Every ejaculation means an orgasm.
While that may be far many (or most, I don't know) men, the fact is that it ain't so. If I had an orgasm for every time I've come, I'd have a big sloppy grin.
Here are a few more:
All gay/bi men are sluts.
Straight men don't like anal play.
All men are obsessed with penis size.
The same goes for breasts. The bigger, the better.
Men don't like foreplay.
All men enjoy having their backs carved by nails.
All hetero men are obsessed with lesbians.
There aren't a lot of sexual areas in which popular opinion isn't wrong.
Neil Stephenson nailed down one of the big reasons for this misinformation in Diamond Age:
Bud's relationship with the female sex was governed by a gallimaufry of primal impulses, dim suppositions, deranged theories, overheard scaps of conversation, half-remembered pieces of advice, and fragments of no-doubt exaggerated anecdotes that amounted to rank superstition.
That's how most men, and I suspect most women, learn about the opposite sex, and in terms of sex, themselves until experience tempers the ignorance.