Ah I found the original quote - I misremembered it as skittles, but same message:

“Imagine a bowl of M&Ms. 10% of them are poisoned. Go ahead. Eat a handful. Not all M&Ms are poison. #YesAllWomen.”

The premise being, of course, that while good men do exist in the world, women have spent a lifetime preparing to meet one who is not.

The original analogy is a box of chocolates, where some are poison. In the original German, it's actually even more cool because the German word for poison is "gift"!

(Also it was originally published in 1930s Germany, and the 'poison chocolate' referred to Jews)