If this is true it just means that the concept of good is meaningless. If there is no example of a bad person, what significance can you attach to good?
I agree with everyone who posted so far. This statement is worse than nonsense. How about a more truthful statement like "Most people are average." At least that's statistically correct and in line with the bell curve.
All people are inherently good, some consistently or habitually use their free will to make bad choices. Each person, simply by being human, has a natural dignity that cannot be taken away.
How about "every person is born good" for a more truthful sentence.. Or "every person here is good"
That would be "Kazdy człowiek rodzi się dobrym" (rodzić = to born) or "Każda osoba tutaj jest dobra" (person = osoba, here = tutaj).
Direct translation for that is "Każdy jest dobry", without "człowiek". (but then, "everyone" always refers to humans, at least right now when there are no aliens or super intelligent animals around, so perhaps everyone should be accepted)
"Everyone is good" can also apply to anything both animate and inanimate as in "I have checked them all and everyone is good"