Clint, I am not advocating such at all with this post, just giving my take on the one experience that I've had with a thermal scope....
I was hunting last year with PDK as he had acquired a used thermal scope that he mounted on a wooden 'gun stock' he cut out just for 'aiming'. He showed it to me one evening as we looked in places that we knew held deer near the ranch house and it was cool to see that.
It was also cool to know, after the fact, that Patrick got to enjoy my stalk and shot even though I never knew he was going to follow me after I got out of his vehicle. He walked behind me after I got way out in front as he knew exactly where I was going, where the hogs were going to be, and where to set up downwind as not to spook them. Patrick used that thermal scope to watch me sneak up on the hogs which he could see also. At one point the hogs an I both were in his view. He got to see me draw and hear the hog make its death squeal. I thought that was cool and he was so excited about it that he might as well have killed the hog himself.
Then two nights later, I went with him to look for his hog and we did the normal look, track, look track and blindly busting through thick TX trash to no avail. We had really given it our all, and if anyone has tracked with me that's the only way I go. I said to Patrick, "why don't you take that scope thing and go up to that tower stand and have a look just for kicks". Sure enough the hog was still warm enough that he saw it over a 100 yards away. We were both tickled that the hog had been recovered.
I don't really see any ethical issue with that use.
However, if you shoot an animal and immediately use a thermal scope instead of woodsman ship.... well, that's another story. Same with lighted nocks, I have been in on two of those and one was a last ditch effort due to total lack of blood, the other, after 3 hours of tracking lead me to the animal only 6-8 yards ahead which I feel I would have found anyway, but the nock did give way to the arrow, and the arrow was still in the javie.