Spewage is the generalized material that is emitted when an entity spews nonsense or vitrol. An example of the associated imagery would be when the worst stereotype of one's political enemies enters a discussion and projectile vomits on everyone involved. Highly disparaging of the target.
The word also readily forms compounds:
Spewage ratio; Conceptually similar to signal-to-noise ratio, but with the connotation that the spewage would not be interesting anywhere.
Spewaging; Distinguished from "Spewing" by the fact that "Spewing" does not require negative connotations. Spewaging by contrast demands the harshest of negative connotations.
[UPDATE: +Ken Barber suggests "Spewtard"
Spewtard; One who spends most of their time spewaging.]
I did not originally come up with this as a modification of "Sewage", but the serendipity is most welcome.