:wasalamex
I know where you're going with this, knew it from the start. However, Your question is irrelevant as it does not even relate to the issue on hand. He's innocence or sins has nothing to do with it.
Where am I going with this? It has something to do with it actually. You obviously think there is something wrong with being a gov't stooge, since you see this as a valid reason to not pray behind a khateeb. You link to IslamQA in your user title, so I assume that you take that as a reputable source? Well, according to Shaykh Salih al-Munajjid (and also the favoured opinion of shaykh 'Uthaymeen rahimahullaah), the correct opinion is that you can pray behind a sinner, and the reasons for this are:
1 – The general meaning of the hadeeth of the Prophet (peace and blessings of Allaah be upon him): “The people should be led in prayer by the one among them who has most knowlegde of the Book of Allaah.” (Narrated by Muslim, 673).
2 – The specific meaning of the words of the Prophet (peace and blessings of Allaah be upon him) concerning oppressive leaders who lead the prayer at the wrong time: “Pray the prayer on time, then if you come to them at the time when they are praying, pray with them, and it will be a naafil prayer for you.” (Narrated by Muslim, 648). And al-Bukhaari narrated: “If the imaam leads the prayer correctly, then he and you will receive the rewards, but if he makes a mistake (in the prayer) then you will receive the reward for the prayer and the sin (will be his).” (Narrated by al-Bukhaari, 694).
3 – The Sahaabah, including Ibn ‘Umar, used to pray behind al-Hajjaaj, and Ibn ‘Umar was one of the keenest of people to follow the Sunnah and pay attention to it, and al-Hajjaaj was known to be one of the most rebellious and sinful of the slaves of Allaah.
It might also be said that everyone whose prayer is valid, it is also valid for him to lead the prayer. There is no evidence to suggest that we should differentiate between the validity of the prayer and the validity of leading the prayer, because if a person commits a sin, he does so for himself, but this is merely theoretical. See al-Sharh al-Mumti’ by Ibn ‘Uthaymeen, (4/304).
Source
And if you do not consider it to be a sin, then there is no issue here then is there? If 'Abdullah ibn'Umar radhiyAllahu 'anhu would pray behind the likes of al-Hajjaaj, the rebellious tyrant, then I do not see why there is a need to spread fitnah? Who do you consider to be more evil, al-Hajjaaj or this supposed gov't stooge? And who do you consider to have more hikmah, you or 'Abdullah ibn 'Umar?
And by the way, if you consider Musharraf to be Muslim, you should know that it is the manhaj of the people of the Sunnah to not spread the faults of the Muslim rulers, aslong as they establish the prayer. Unless you think Musharraf is a disbeliever, then that's another issue.