Not at all true. The simple fact that we're born with two legs is proof that massive amounts of information about our surrounding world is already encoded into us before birth. It took millions of years for life to develop this novel mechanism for traversing this planet.
This, of course, extends to our minds as well. Simply the structure of our brain has an immense impact. Even if you don't believe that our neurons are pre-trained to know some things, you'd have to admit that our brain is wired in a way that allows us to learn quite efficiently in this world. But psychology is quite complicated, so it's hard to say what exactly is nature and what nurture.
Technically, when first life began, it really was without knowledge. Over time, organisms learned and adapted more and more to our environment, both physically and mentally.
This really depends on where you draw the line between knowledge and non knowledge. Our entirety scientific body is the best explanation we have for the phenomenon we as a social species have observed. Much of what we call 'knowledge' - like maths or physics, is actually human produced culture (in that it is taught after it has been discovered). It is subject to being incorrect (although it would take a very powerful set of observations, deductions, definitions, and measurements to prove it incorrect).
I think honestly, the line between nature and nurture really depends on what you believe makes you human, conscious, and existing with awareness. You can technically define the entire existence of the universe as a process of changing states of information (some of which may not be measurable).
OP's claim is quite naive. Even if you haven't read anything on this, when you have a child you'll immediately understand how much information they have out of the box. Some well-known examples:
* Language learning. Chomsky's Universal Grammar (http://en.wikipedia.org/wiki/Universal_grammar) posits that we are born with a language faculty that has a lot of switches about language, we just set the switches by being exposed to a particular language.
Some people believe that young children know more about The Truth in a spiritual sense than adults. They just have it forced out of them by the time they grow up.
Is that really true? A google for "babies are hardwired to" brings up a enormous number of results.