You're completely right. That's so sad and rather disturbing about rumors and society. People believe what they want to believe. And they'd really like things to be that easy (or shaming, like Lucidity said).
: It's impossible to get pregnant on your period.
Fact: Though the probability is a lot smaller, it's not impossible. In fact someone women are more fertile around their periods.
: Men have to have regular sex to be healthy and that's why they cheat when their partner doesn't 'put out' regularly.
Fact: Though it's suggested that they "clear their system" and ejaculate every now and then, men are a lot tougher than that and this was created just to defend those cheaters out there. Masturbation is always an option.
: Butter makes a great lubricant.
Fact: Uh, everyone at EF pretty much knows this one. Butter is a food item and not a natural lubricant. It will change the pH balance of your vagina and increase your risk (if not guarantee) an infection. Not to mention that as a dairy product, it can spoil and go bad pretty quick and why would you want that down there