The problem is what scale you have to declare a ruler a bad ruler-
Example say zardari- can you prove- have solid proof to fight against him-
how can you be sure he is really bad- not victim of propaganda-
you think he is bad start a rebellion against him- can you ever find out what value good or bad he has infornt of Allah?-
Salman Taseer- The qadri guy had his genuine reasons to kill an acting governor of a state-
so answer me this can an individual or group them are worthy enough to judge other people?-
By that logic there will be bloody mess in every corner/ street of Muslim world-
thats why Allah has kept such matters in his own hands- He is the only one that can judge-
How about forget what i am saying- Tell me a Quranic verse saying Fight violently against an unjust corrupt or bad ruler-
Here is a translation of the verse you quoted in urdu-
Surah Ash-Shu'araa - Translation of Quran in Urdu From Kanzul Iman