Lord Raith is a *user* of Outsiders, but it doesn't necessarily follow that he's opposed to the work of the Venators -- in fact, he could benefit greatly from their work, as long as they aren't erasing *his* knowledge.
In Blood Rites, Harry Dresden describes the kind of magic Raith's little coven of ex-wives uses as being like a vending machine, which can be depleted. He talks about the White Council sometimes going in the opposite direction from the Venators -- deliberately spreading around knowledge of a ritual, so that too many users will try to draw on it, not giving it time to recharge between uses.
So Papa Raith's goals would be that (1) he has the ritual in his library and (2) no one else does. Lara Raith in the Venators would be in a good position to serve both goals.