Historian: Those who claim that Shakespeare did not write the plays commonly attributed to him are motivated purely by snobbery.
Conclusion
People who say that Shakespeare didn't write the plays attributed to him are motivated purely by snobbery.
Evidence
Shakes was the son of a glove maker, whereas the other potential authors of "his" plays were aristocrats, and many of the people arguing that these other people wrote S's plays are the descendants of these aristocrats.
Evaluate
Given this evidence, how could we argue that "people claiming S didn't write all the plays commonly attributed to him are NOT motivated purely by snobbery (they might be motivated partially by snobbery, but they're motivated by something else as well).
First of all, are these people even aware that S is the son of a glove maker? They can't be using this against Shakes if they don't know it.
Secondly, it says that many of the people claiming S didn't write all the plays are descendants of aristocrats, but that leaves open the possibility that many others claiming the same thing aren't descendants of aristocrats. They might be descendants of lower class people and have no "snobby" motive at all.
Finally, it doesn't seem like this argument gives much of a charitable reading of the opponents' position. What is their evidence for thinking Shakespeare didn't write all these plays?
Goal
Since the conclusion so dismissively says that "these claims are 100% snobbery", we just need any answer that allows us to argue that at least part of this isn't snobbery, it's coming from some other source of evidence or motivation (maybe it's coming from jealously)