The Harm Principle and a Grey Area

When discussing law and the harm principle, a society based on such founding can, over time, easily be "re-interpreted" to further an oppressive cause or agenda.

An example would be the idea of disease and, perhaps, intent. Can the transference of something, uh, 'physically un-physical' be in violation of the Harm Principle? If not, should the idea of intent be a principle of examining cause and effect?