Born as a sinner?

Something Baptist preachers are fond of saying is that "people aren't sinners because they sin; they sin because they're sinners."

Last I checked, the definition of "sinner" was "one who sins." How could one possibly be a sinner before s/he sins? The typical answer is that "man is born in sin."

But I don't think this is supported biblically. Undoubtedly we are all sinners; the Bible clearly states and empirical evidence eloquently demonstrates this. We have also inherited "sin nature," or the propensity to sin. I have yet to see an indication, however, that we have actually inherited the "sins of our fathers." I do not believe that we are actually sinners before we have sinned. I do not believe that we are born guilty.

The definition of guilt is "the fact of having committed a breach of conduct especially violating law and involving a penalty." If I - personally - have never "committed a breach of conduct," then I am not guilty. I am not a sinner because Adam, my great-great-ever-so-great-grandfather sinned; I'm a sinner because I sinned. It is my own sin, not Adam's, that makes me a guilty sinner before God.