Fighting the unbelievers and treating them harshly is one of the requirements of religion. - Ahmad Sirhindi

The honor of Islam is in the degradation of unbelief and the people of unbelief.

The real purpose in levying jizya on them (the non-Muslims) is to humiliate then to such an extent that, on account of fear of jizva, they may not be able to dress well and to live in grandeur. They should constantly remain terrified and trembling. It in intended to hold them under contempt and to uphold the honour and might of Islam.

Before that kafir [Guru Arjun Deva] was executed this recluse [meaning himself] had seen in a dream that the reigning king had smashed the skull of idolatry. Indeed, he was a great idolater, and the leader of the idolaters, and the chief of unbelievers. May Allah blast him! The Holy Prophet who is the ruler of religion as well as the world, has cursed the idolaters as follows in some of his prayers – “O Allah, demean their society, create divisions in their ranks, destroy their homes, and get at them like the mighty one.”
It is required by religion [Islam] that jihad should be waged against the unbelievers, and that they should be dealt with harshly… It is obligatory on Muslims to acquaint the king of Islam with the evil customs of false religions… Maybe the king has no knowledge of these evil customs… Some Ulama of Islam should come forward, and proclaim the evils present in their (unbelievers’) ways… It will be no excuse on the Day of Judgment that they did not proclaim the tenets of the Shariat because they were not called upon (to do so)…