There are numerous occasions when County sides have beaten full strength touring sides. The 2009 Durham was a strong outfit by any County standards and given conditions at the Riverside are generally alien to touring sides history suggests they'd have a very good chance of being victorious.
As to Onions only he himself knows whether his comments were intended to be provocative. As an experienced cricketer, however, he would know that he should be guarded in his comments for fear of being misinterpreted unless of course, he was intending being provocative. He clearly has a grievance which is understandable.