Yes.
Langtree might not be wrong, we saw it in Molly, and Harry at times, though Eb managed to drill enough morals into his head that he usually checks himself, often only just.
We should note, too, that at the end of
Battleground, Ramirez accuses Harry of having slid off the path and toward monster-ness, without even realizing it. That his bondage to Winter makes him a proto-monster, more or less. Before we assume Ramirez is wrong, we should remember that Harry, under the influence of the Winter Knight mantle, came extremely close to murdering Rudolph. If Sanya and Butters hadn't been there to save Harry, he probably would have. I remember, too, that afterward the Winter Mantle was able to annul the pain of all Harry's wounds...
except the burn from where he touched Butter's Sword.
Harry has a choice, he still has his free will, even with the Mantle. But that automatically doesn't mean he'll make the right choice. Harry came very close to proving Ramirez right in
Battleground.