A Muslim judging between right and wrong is not the same as Allah’s judgement and both should be kept separate from each other. Allah knows what people think and what their intentions are. We don’t. This is why we follow the rule set out by Prophet Muhammad (SAW):
Narrated By Um Salama : Allah’s Apostle said, “I am only a human being, and you people (opponents) come to me with your cases; and it may be that one of you can present his case eloquently in a more convincing way than the other, and I give my verdict according to what I hear. So if ever I judge (by error) and give the right of a brother to his other (brother) then he (the latter) should not take it, for I am giving him only a piece of Fire.” (Sahih Bukhari – Book 089, Hadith Number 281) [Emphasis added]
Also Sahaba (RA) also stood against the false beliefs and practices prevalent in their society, which were carried out by their relatives, friends and fellowmen who also claimed to be on Deen-e-Ibrahimi. Due to this modern age of being "politically correct" and a myriad of non judgmental philosophies like Zen, buddhism etc people have absorbed it and are not ready to criticize and condemn the Islamic injustice and wrong that is happening around them. So does not every Muslim has every right to judge between right and wrong as long as he does this in the light of the Qur’an and Hadith?