I think you understand the general idea.  The phrase "you can stand only so much" means "you can tolerate only a limited amount."  You could say "I can't stand so much rudeness," and the meaning would be similar, but not quite identical.  In the example you gave, the emphasis is on the extent of the writer's ability to handle a supervisor's rudeness.  Your suggested correction would instead emphasize that he or she cannot tolerate a lot of rudeness, rather than that his or her ability to tolerate it has limits. Similar, but not exactly the same. 

Thank you, Craig. I got it! And Is the meaning behind the original sentence that if one man had decided to stay, he should have had to tolerate more rudeness from his supervisor?