First of all, it begs the question to assert that the NO is mutilated in such a way as to invalidate the form, let alone the intention of "doing what the Church does."
Well it begs the question in the sense that they've made that case elsewhere and weren't addressing that here. I (partially) agree with them that the English mistranslation of the consecration of the wine renders the validity of the Mass positively doubtful.
Secondly, it is undisputed that "This is My Body" alone suffices for the conversion of the bread. Even if a priest were to stop there, the bread would be consecrated.
Actually, I recall that not to be so from my seminary days. There were cases in the sacramental theology manuals about the hypothetical case of a priest who, say, dropped dead after consecrating the bread and whether it would be valid. Not a few theologians felt that it wouldn't be.
Their reasoning has absolutely no foundation in sacramental theology and is in fact quite dangerous. They offer no citations, but just vomit forth whatever comes to their perverted minds, think that they are teaching the world the true Catholic faith when in reality they sound like school children.
I don't think that their argument is that bad. Where it falls flat is where I told you. Let's say a priest were to intend up front to mutilate the words regarding the consecration of the wine so as to render that part invalid. In so intending, he would not be intending to do what the Church does. Where the problem comes in is that the priests who offer the NOM have no such bad intention. So their argument evaporates.
Instead of being so dramatic, can't you just say that their argument is wrong? You're often way too bombastic for your own good.