Actually, the chemical aggressiveness of soft corals and zoos varies tremendously from species to species and genus to genus. Some sarcophytons will chemically attack stony corals if they sense their presence, othes might not. It really seems to be a hit or miss situation, although the Borneman book does have a chart of relative toxicity among several common aquarium species, and it's worth looking at.

Regarding the handling of zoos, the most dangerous polyps that I've heard of are the palythoas; in fact, these have been traditionally used in neurotoxins on poison darts. So the next time a pygmy aims his/her blowgun at you, you feel a sting, then get lightheaded, you can pass out with the satisfaction that you know what's causing it!