What is the appropriate response when non-Muslims ask why they are prevented from entering Makkah?

The Muslim responds that Allah Almighty has forbidden enabling polytheists from entering the Sacred Mosque (Al-Haram (definition)), and He justified this by stating that they are najas (unclean), for their creed is corrupt and they do not purify themselves from impurities. He cited the Almighty's saying: ﴿O YOU WHO HAVE BELIEVED, INDEED THE POLYTHEISTS ARE UNCLEAN, SO LET THEM NOT APPROACH THE SACRED MOSQUE AFTER THIS YEAR OF THEIRS.﴾ Sheikh Rashid Rida said: "The polytheists are najas, corrupt in belief, they worship filth and follow superstitions, and they do not purify themselves from impurities and sins. The attributes of najas have become ingrained in them, both physically and spiritually, so do not enable them after this year from approaching the Sacred Mosque." This is the evidence for preventing polytheists from entering Makkah, and its reason is their being najas in belief. This is the view of the majority of scholars and it is the preponderant opinion, even though the people of Kufa permitted a mu'ahid (a non-Muslim living under a treaty with Muslims) to enter the Sacred Mosque.