Part 3. "Darwin's theory doesn't explain where life came from"
The proper response here is really "well duh, your right." Darwin's origin of species does not attempt to explain the origin of life. The theory only states that over time, the genetic structure of populations of plants and animals will change. The fact that evolutionary theory doesn't address the origin of life has nothing to do with its validity. While there are those who have theories about the origin of life, no biologist worth their salt will tell you that they know for a fact where life came from. It remains one of the big unknowns. While I don't buy into this idea, its reasonable to argue that the creator made life, then used evolution as tool to get us to this point.
Another bizzare argument I was given one is that "Darwin was a racist." My answer there is two fold. First, Darwin was a man of his time, no more or less racist than your typical Englishman the the late 1800's. The second part has to be "and how does that bear on his theory?" For arguments sake lets agree that had he lived in the American south, he'd have been a KKK grand wizard, while this would have made Darwin a disagreeable chap, it would have done nothing to reduce the value of his theory.
Finally I often hear "What about Social Darwinism, Hitler liked his theory..." Much like the when people of my ilk say things like "religion is responsible for more wars than anything else combined" and we hear back "its not God's fault that people twist His words", how is it the fault of evolutionary theory that some twisted SOB's will misuse it?