Have you ever tried freshly made soy milk (i.e. made the same day from just soy beans and water in the traditional way) ?
You are describing a placebo. You tricked yourself into thinking it's fish (if anything it's algae/carageenan) and that you don't like fish (algae). You can train yourself back and enjoy the benefits of soy milk.
It was like a negative aha-moment, a taste that was always there but I never noticed it, when it finally clicked, and I found out it was a fishy taste soy milk pretty much died for me.