I agree that is generally sound reasoning; however, it is a fact that all the early mss come from Alexandria where allegorical interpretation was practiced. The churches in the Byzantine empire, Carthage, Ethiopia and Syria all practiced literal interpretation, and treated God's word with reverence and respect. Where the Byzantine, Carthaginian, Coptic, and Syriac texts are in agreement and are contradicted by two questionable texts from Alexandria; it seems possible if not likely that the disputed (so called) additions were actually dropped from the Alexandrian text.
1. Are you sure that all early mss come from Alexandria?
2. Can you define what you mean by allegorical interpretation and why do you think it was practiced there?
3. Can you define relationship between allegorical interpretation of the text and willfull alteration of the text?
4. Can you give some examples of such alterations because of allegorical interpretation?