who should be named as the defendant in the original motion?
There is no defendant "to a motion". There is(are) defendant(s) "to a complaint", the starting point of judicial proceedings which usually entail a number of motions, hearings, conferences, a trial, and so forth. The defendant to the complaint is only the corporation you intend ...
If someone needs slightly more explanation, this (i.e. plaintiff choosing meaning of "the sting") has been the procedure for at least two decades in Australia, as explained in a
2002 article; furthermore such meaning may/does include inferences one could draw from the material:
defining the sting lies in the hands of the plaintiff, the defendant ...
Because they lost
The procedure was espoused by Aesop in The Fox & the Grapes - don't listen to the loser when they complain that the game was rigged.
Also, don't complain that "that's not how they do it in England" - how they play they game in other places is irrelevant.
The plaintiff sets the terms of the case
Defamation is rarely about out ...