From a flavor perspective, black would be a color that would allow you to dump your poison onto others, or manipulate it in a similar fashion. Not necessarily prevention, but in essence the same or worst.
In my book, the damage is part of the design space. Sure I give some design space up, but it is worth it for the flavor and interactivity.
Also, I was responding to your claim "corruption=1 damage in counters" was parasitic.
It's not. Not in any sane* way of defining it.
*I could just as easily argue creatures with X is parasitic if I only insist on attacking with creatures that have X.
And I know why I'm doing it that way. Because it's meant to show how the Inquisition burns people and their instruments - that's the flavor. But even on a most basic mechanical level (modulo flavor), no one else found this problematic. Well. Almost no one
I still have the problem with "They never did it, so they will never do it" mentality. R&D shifts their position all the time.