The entire canon has been added to and modified for thousands of years... There's no reason to harp on them for this any more than there is to harp on scribes 1000 years ago. Even if one were to believe the bible is inspired, there is no was to distinguish which parts are and which aren't. Bart D. Ehrman has done a lot of great work on this.
In regard to Matt 8:1-11, it directly contradicts the WT's shunning policy. If Jesus were real, he wouldn't have participated in shunning. Plain and simple. These verses were an easy choice for removal by the WT.