It may be argued (as I have) that signing the MD was naïve, imprudent, unhelpful, and at best meaningless. It may also be argued that this usage of "Christian" creates a troublesome ambiguity. But this assertion, on the basis of its use of "Christian," that it actually compromises the gospel is simply unsustainable. "Christian" doesn't always mean the same thing. And it's not just me saying that. It's Kevin Bauder writing here:
[T]he term Christian is used in more than one sense. In the strict and proper sense, it applies only to those who affirm all the fundamentals of the Faith, including the imputation of Christ’s righteousness and justification through faith alone. In this sense, the Roman church of today is not a Christian church and most medieval Catholics were probably not Christian either. In a less technical sense, however, the word Christian can be used to distinguish those who affirm Trinitarian orthodoxy from infidels, pagans, and cultists. In that sense Catholicism can be called Christian, and that is the sense in which the Middle Ages were influenced by Christian categories.