because no one was fighting back?
Yes I admit that was true but the OP was in many ways talking about auto ack.
I caught the task force half way between their port and our field. I knew it would be there as a big CV to CV battle had just ended with both CV's being sunk. Since I launched a PT just prior to the last destoyers re-spawning and was within 1 1/2 sectors of their port I took off hunting.
I paced the task group until I got in front of it and fired four torps directly into the bow of the CV and it went down. I turned to get out ahead again then came back toward the cruiser firing my rockets (and missing), then turned again, lowered throttle, sank the cruiser with my 40mm then killed all the guns on one destroyer with it. At that point I decided I was done but had to go 2-3 sectors to rendesvous with a friendly task force for a landing.
I have used the same tactics on a manned task force though with similar success. The direct frontal (or rear) attack miimizes how many guns that can be brought to bear increasing the likelyhood of survivability. You have to keep a little more distance against live gunners too which makes aiming your torps much more difficult as well and, in fact, I prefer a spread pattern at that point to account for someone turning the CV.
Anyway, you can kill a task group with a PT. PT's are fun.