Curator note:  I changed the title of this topic to make it easier to find as a reference later.  The original title was:
Something from the beginning of Cold Days that really bothered me(spoilers, duh) ^-Serack

When he's laying down the law to the winter court:
My voice echoed throughout the whole chamber as clearly as if I’d been using a PA system. “All right, you primitive screwheads. Listen up. I’m Harry Dresden. I’m the new Winter Knight. I’m instituting a rule: When you’re within sight of me, mortals are off-limits.” I paused for a moment to let that sink in. Then I continued. “I can’t give you orders. I can’t control what you do in your own domains. I’m not going to be able to change you. I’m not even going to try. But if I see you abusing a mortal, you’ll join Chunky here. Zero warnings. Zero excuses. Subzero tolerance.”
I paused again and then asked, “Any questions?” One of the Sidhe smirked and stepped forward, his leather pants creaking. He opened his mouth, his expression condescending. “Mortal, do you actually think that you can—” “Infriga!” I snarled, unleashing Winter again, and without waiting for the cloud to clear, hurled the second strike, shouting, “Forzare!” This time I aimed much of the force up. Grisly bits of frozen Sidhe noble came pattering and clattering down to the ice of the dance floor.

When I first read this I did a mental double-take. Harry committed murder there. Seriously, he straight up murdered a sapient being for the crime of disagreeing with him, and somehow it's okay because it was a Sidhe, not a human. And nobody calls him out on it. There have been other instances of speciesism in the series, but this takes the cake.