You are probably familiar with this comic which illustrates the possible ambiguity caused by leaving out the Oxford comma:
However, this strikes me as plain wrong. I thought comma would not be used to delimit the name of/word for a group and the listing of its constituents. The sentence given as an example on Wikipedia regarding the usage of the em dash indicates one would use either an em dash or a colon for this purpose:
Simple equivalence (or near-equivalence) of colon and em dash
- Three alkali metals are the usual substituents: sodium, potassium, and lithium.
- Three alkali metals are the usual substituents—sodium, potassium, and lithium.
So one would think that, in order to convey what is portrayed in the second picture in the comic, the sentence should be:
We invited the strippers: JFK and Stalin.
We invited the strippers—JFK and Stalin.
So, with all that said, my question is:
Is the sentence without the Oxford comma considered ambiguous because too many people are not familiar enough with the rules of punctuation of the English language, or are the rules laxer than I thought and it is valid to use a comma in this case as well?
(Bear in mind—English is not my native language, so the latter may well be the case.)