I dont really agree.
I think we are worse. A disease does not attack itself, a flu cell does not naturally want to destroy another flu cell. Diseases are systematic and the cells work as a part of a whole. They do not try to out do one another and have no ulterior motive other than the survival of the whole, not each individual.. Humans are not like this, they are selfish and want what is best for them individually or in a small group (family, business, etc), not what is best for the whole.
Humanity is however, by definition, a parasite.
"An organism that grows, feeds, and is sheltered on or in a different organism while contributing nothing to the survival of its host."
We really contribute nothing to the survival of the planet, in that, our existence does not benefit the planets survival in anyway. Now this is not necessarily a negative thing, as the same can be said for any living creature on earth, and in fact the same can be said for the planet in the context of the universe.