"But I was born with these feelings. That means it can't be wrong!"
There is a lot that could be said but lets keep it simple.
"If I'm born with the natural inclination to lie or steal, does that make it okay?"
The truth is that we are all naturally inclined towards evil from birth. Whether something is right or wrong is independent of what is "natural". Perhaps this is what David is talking about in Psalm 51:5