Intellectually, I certainly understand that their pain does not carry with it the emotional context that a human's or other higher animal's pain does and I don't worry about a tick's feelings when I mash them. It seems to me to be largely unnecessary to clean them while they struggle and it bums me out for me to do it. I know that lots of people clean their fish straight out of the livewell ; I can't change that and I try not to worry about things I can't change. I don't know if I could argue that it is unethical for you to do so, but I don't think anyone could argue that it is kind to run a knife through them while the are alive and aware.
I fully acknowledge I'm tender hearted about stuff sometimes, but me putting my fish on ice before I fillet them shouldn't make anyone else lose sleep either.