Defining "yinzer" to only include "the bad ones" is bound to cause confusion since many people use the term more broadly. In fact, see this Wikipedia page:
http://en.wikipedia.org/wiki/Yinzer
Of course it literally refers to people who speak in the Pittsburgh regional dialect, which is not inherently pejorative. As reflected in that article, it has really only taken on a pejorative connotation more recently, and it is far from clear that to the extent people associate certain negative traits or behaviors with the term, that is as a limiting definition. The alternative is such people are simply engaging in a negative stereotyping of the whole group, which again is a form of bigotry.
Moreover, such lists are often subject to over-universalization. For example, someone could be super into the Steelers, and even (horrors!) DVE. But they could also be not at all racist, like living in the City, and so on. And if someone then starts talking about hating yinzers, and making fun of liking the Steelers and DVE, are they supposed to understand the speaker doesn't really mean them, but just those other bad yinzers who are also racists and such?
The bottomline is yinzer is one of those class/ethnic terms that can sometimes be used neutrally or positively without harm, but as soon as you start using it negatively you are very likely going to cause unintentional and unjustified offense--unless, of course, you actually embrace being bigoted.