I honestly don't understand how a
serious Cowboy fan can have this point of view. I'm not talking about
casual Dallas fans who occasionally watch games, but fans who watch every game and even join forums regarding the Dallas Cowboys.
You're right, his record against "winning records is not very good", but that's because his own team "is not very good". It has little to do with Romo's individual performance, and more to do with his team's performance as a collective group. I'm probably about to drop some earth shattering news here that many didn't know, so don't be shocked too much (/sarcasm) ... Football is the ultimate team sport, the team with the best 46 man roster on game day wins most of the time, not the team with the best QB.
Also, here's an article from 2012 that talks about Romo's INDIVIDUAL performance against "teams with winning records" and "bad teams", feel free to educate yourself more regarding that particular topic. It has some very telling information, like how Romo has a career 96.4 QB Rating against teams with 9 wins or more.
Article
*The article is from 2012, so there's some missing data* -
http://www.bloggingtheboys.com/2012/6/19/3096499/tony-romo-versus-quality-opponents-what-the-numbers-tell-us