No, that's silly. How can it possibly destroy his argument when he makes the exact same point four verses later? The deletion (or rather, the removal of the later addition) has simply to do with what the earliest manuscripts say, and has no theological 'agenda' or even impact on the rest of the text. Worth pointing out that there are other readings that are different even more, and instead of "walk after the Spirit" say "do not walk after the flesh". Clearly, the additions are taking their cues from v. 4.