Taqiyah (dissimulation or quietism) is a strategy for emergency situations and it does not mean weakness, fear and conservatism. In fact, it is often used as an effective means to combat tyrants, oppressors and the unjust.
What is the difference between Taqiyah on the one hand and telling the truth to an oppressive sultan, hypocrisy, humiliation and misery, enjoining the good and forbidding evil?
Taqiyah (dissimulation or quietism) is a strategy for emergency situations and it is meant to protect human forces and not to endanger Momeneen [believers] in petty and trivial matters. The principle of Taqiyah is a part of the religion of Islam; it is rational and initiated by the Qur'an, confirmed by the traditions of the Prophet (S). It is used as a rational and logical method by a believer who is in the state of combat against his mighty enemy.
Depending on various situations and occasions, Taqiyah sometimes becomes obligatory, sometimes it is haram and other times it is simply allowable. Taqiyah becomes obligatory when one's life is at risk and it is haram when it may cause falsehood and evil to spread and people to go astray and injustice to be consolidated.
Munafiq (hypocrite) is a religious hypocrite who outwardly practices Islam while inwardly concealing his disbelief whereas in fact Taqiyah is defined as the opposite of Munafiq. Showing oneself as being oppressed and humiliated takes place at a time when the individual embarks on concealing his beliefs owing to fear or cowardice whereas Taqiyah does not mean weakness, fear and conservatism. In fact, it is often used as an effective means to combat tyrants, oppressors and the unjust.
When it comes to enjoining good and forbidding evil, there is no doubt that one must use this method of promoting virtue with calculation, logic and in a thoughtful manner. Scholars who have studied in social areas, have said that the secrets behind the extinction of Kharijites in the early period of Islam was that they did not use logic in enjoining good and forbidding evil. They believed that it was not necessary to use Taqiyah as a tactic to enjoin good and forbid evil.
Source: http://www.islamquest.net/en/archive/question/fa12072