Is there an example of a physical skill like Might being used to make a social attack in this way? It feels like something I might do in SotC, but not so much DFRPG. If someone used magic this way, you would roll the Evocation v. Conviction to determine the amount of social stress? My mind is breaking on the amount of social stress you could dole out with a 30 shift thaumaturgical pantsing ritual.
Again, not arguing that wizards
should run around pantsing people and dealing ridiculous social damage just arguing that there's plenty of thematic and RAW justification for it. At my table we have a gentleman's agreement that wizards won't start throwing around 8-shift social attacks (in fact I don't think the wizards have ever thrown a social attack, they mostly maneuver and block) so as to maintain the equality of the social conflict. But mostly what I'm saying is that I see that as a house rule (and a really justified house rule at that) not as RAW.
As for how I would deal with it, I would have them defend with whatever social skill they could justify, Discipline to keep their cool, Presence to pull it off with dignity, Deceit, Performance or Rapport maybe if they wanted to play the wounded puppy. In the social arena it's all about face, so it's not about them resisting the pantsing, it's about how they deal with the situation afterwards and how people see them as a result.
As for lawbreaking via sponsored magic there are a couple of layers to my thoughts on the power itself. Firstly when you take lawbreaker part of it is the representation of what doing something like that with a part of you that represents the core of what you are (I.E. Your magic) actually does to you. Seems to me that isn't applicable when you aren't using your magic.
However in my opinion there is more to the lawbreaker power than just that one aspect. There is also the part that everyday mortals have to worry about. The part where people aren't programmed to be able to kill/invade/transform one another in such an intimate fashion. That doing so requires justification in one's mind, and once justified it gets a little easier. Once it's easier maybe it requires less justification and you start doing it for other not so good reasons, and eventually you're a madman, killing/invading/transforming just because it has a slight benefit. Seems to me that sponsored magic wouldn't make a difference in that case but that kind of thing would also depend greatly on the person, how they dealt with things and who they were. Also there's the part about a powerful organization trying to kill you.
Finally what I was trying to say when I said that kind of thing might make people angry was not that it might lead to lawbreaking but that it would be an unpredictable block in some cases. What may prevent some people from shooting might also drive others to further hostility. If there was someone there who was very angry at the christian faith they might take that kind of imagery in an entirely different manner than was intended and become more belligerent. Not saying they'd shoot you outright, but they'd definitely be less interested in talking. Of course as a GM the only reason why I'd say that there was someone like that in the crowd was if someone had an aspect that I felt justified said compel.
