I would have to disagree with your disagreement.  I know of no grammar text or style manual in use at my college or private language schools where I have taught that ever states that any punctuation other than the comma is expected with coordinating conjunctions.  You certainly could use a semicolon, but that is usually used with adverbial conjunctions such as "I missed the bus; therefore, I had to walk to work."

 

I agree, of course, about commas and coordinating conjunctions. As I mentioned earlier, though, I do not put so in that category. Way back in the 1950s the textbook I used called so a transitional adverb—in the category with therefore, however, and hence. In other words, using that approach, one would indeed call so an adverbial conjunction. The authors of the book I used wrote “The term ‘conjunctive adverb’ has been discard in this book because of its ambiguity….” My guess is that more and more people will be using only a comma before so that it will, in effect, become a coordinating conjunction. As a matter of fact, I am reading a book now whose author does not use either a comma or a semicolon in those situations!

Gerald