Well, actually Ibn Taimiyya legitimised jihad against the Mongol rulers, who were Muslims at that time. He’s quite well known among historians as an anti-Mongol theologian. Some even accused him as deviating from ahl al-sunnah wa al-jamaah by waging war against muslim rulers, since it is deeply established in Islam that Muslims are not allowed to do that, so long as the rulers do not publicly apostatize and prayers are still established. So Yahya Michot went on to defend Ibn Taimiyya’s ijtihad saying that the revered theologian’s situation was entirely different- his fatwa was against invaders, not typical rulers. Moreover, not only that they are new Muslims (with highly precarious and questionable conviction), the Mongol King at his time, Oljaytu, was a Shi’ite.
What about the status of domains that were once (and maybe until now) playing a vital role in Muslims’ attitude towards a certain region? Imam Malik, al-Shafi’e, ibn Hanbal, al-Shaibani and Abu Yusuf al-Ansari (students of Abu Hanifah) ruled that only regions governed by Islamic Law can be awarded dar al-islam, not taking into account the make up of the populace. While they could be right in the midst of the air that they breathe, Imam Abu Hanifah does not accept the status of dar al-harb be given to any areas unless three conditions are violated, one of them being the right to practice Islam free and securely.
As an extension, Ibn Taimiyyah and many later scholars now favour a moderate judgment, giving the status of dar al-islam and dar al-harb mainly based on the security to practice Islam in the area. This is why we heard Hamza Yusof of America asserted that he prefers to live in the
This subject is also dealt (in very detail) in Tariq Ramadan’s To be a European Muslim.