^ Pretty much that.
The way I see it:
- Renfields viewed under the Sight are monsters and completely inhuman; they have had their free will burned out of their psyches by Black Court and replaced with bloodlust and rage.
- have had their free will burned out <-- that's the key phrase. You can't break a Law by killing a vampire or a Fae because they ostensibly have no free will.
- Harry killed the Renfields in Mavra's by using wind or a spirit shield (I forget) to blast their napalm back at them...that act has been debated up and down the forum but I say if it was two random mooks, Harry's got another Lawbreaker notch in his belt--Harry knew for a fact, or was as sure as he could be, that those men would burn to death before casting that spell. Therefore the only thing keeping him from being a Lawbreaker is that they aren't considered Mortal for the purposes of Lawbreaking.
Of course....Wardens will have a problem with you if you thrall them for yourself, might not be okay with the "free will" argument, etc.
Go with what the table consensus is.