Oh hell no.
Kincaid was insisting that he was a vanilla mortal for the entire scene, he was effectively saying "you're human and I'm human as well" when he said that.
I know it's probably soft, any theory based on any fact other than a WOJ or the word given in text from a being who is known to be unable to lie is subject to colouration as it is seen and heard through the eyes and ears of one Harry Dresden. Conversations held with other characters may similarly contain obfuscation and misdirection if not outright lies.
I take it that we read that passage entirely differently:
“... You're a liar”
“Excuse me?”
“I said you're a liar. I saw you fight at Wrigley, Kincaid. You fired a dozen shots, on the move and dodging bad guys the whole time."
This I took to mean that everything before Harry called Kincaid a liar to be false, Kincaid does not deny the lie, he redirects. When he says he's just as human as Dresden is, I take this to be the only true statement he makes in the conversation, if for no other reason than that is the way I'd do it for dramatic flair – it makes for good storytelling (plus, Kincaid is a prick, I could see him saying something like this just to say “I told you so” later). If I’m right about Kincaid's statements in Blood Rights, then: if Kincaid is a scion (which defines him as not fully human) Harry must in turn have something unnatural in his bloodline. Unless I have evidence either of Harry's family tree or a WOJ saying I'm wrong, then 2 of four possible cases for this argument are equal.
1.) Harry and Kincaid are both not fully Human {x}
2.) Harry is fully human and Kincaid is not {x}
3.) Both Harry and Kincaid are fully human
4.) Harry is not fully human, but Kincaid is
