In The Name of Allaah, The Most Merciful, The Bestower of Mercy.
Firstly: We repeat once again the fact that rebutting false beliefs, ideas and views does not necessitate bad behaviour, rather Muslims are commanded to behave well towards others.
Allaah [The Most High] said: [ قُلۡ يَـٰٓأَهۡلَ ٱلۡكِتَـٰبِ تَعَالَوۡاْ إِلَىٰ ڪَلِمَةٍ۬ سَوَآءِۭ بَيۡنَنَا وَبَيۡنَكُمۡ أَلَّا نَعۡبُدَ إِلَّا ٱللَّهَ وَلَا نُشۡرِكَ بِهِۦ شَيۡـًٔ۬ا وَلَا يَتَّخِذَ بَعۡضُنَا بَعۡضًا أَرۡبَابً۬ا مِّن دُونِ ٱللَّهِۚ فَإِن تَوَلَّوۡاْ فَقُولُواْ ٱشۡهَدُواْ بِأَنَّا مُسۡلِمُونَ –Say (O Muhammad): “O people of the Scripture (Jews and Christians): Come to a word that is just between us and you, that we worship none but Allah, and that we associate no partners with Him, and that none of us shall take others as lords besides Allah. Then, if they turn away, say: “Bear witness that we are Muslims]. [Surah Aal Imraan. Aayah 64]
Meaning: say to the people of the scripture – the Jews and Christians, [تَعَالَوۡاْ إِلَىٰ ڪَلِمَةٍ۬ سَوَآءِۭ بَيۡنَنَا وَبَيۡنَكُمۡ – Come to a word that is just between us and you]- Meaning: Come let us unite upon the statement which all the Prophets and Messengers agreed upon and none opposes it except the obstinate and misguided. This statement is not specific to anyone of us; rather it is something that you and us should establish between us, so this is justice and fairness in debate. Then Allaah explains this and said: [أَلَّا نَعۡبُدَ إِلَّا ٱللَّهَ وَلَا نُشۡرِكَ بِهِۦ شَيۡـًٔ۬ا – that we worship none but Allah, and that we associate no partners with Him]- Meaning: We should single out Allaah in worship, devoting all love, fear and hope to Him alone, and we should not associate anyone as partner with Allaah in worship- neither a Prophet, an Angel, a Righteous Person, an Idol, a Deified image, a living or non-living thing, [وَلَا يَتَّخِذَ بَعۡضُنَا بَعۡضًا أَرۡبَابً۬ا مِّن دُونِ ٱللَّهِۚ – and that none of us shall take others as lords besides Allaah]; rather all obedience is to be devoted to Allah and His Messengers. [فَإِن تَوَلَّوۡاْ فَقُولُواْ ٱشۡهَدُواْ بِأَنَّا مُسۡلِمُونَ – Then, if they turn away, say: “Bear witness that we are Muslims]”. [Tafsir As-Sadi]
Whoever amongst the followers of the previous Prophets comes into contact with Muhammad’s [peace and blessings of Allaah be upon him] message, they must believe in him and aid him, even if they had a revealed book and another Prophetic tradition, just as Allaah [The Exalted] said: [ لَمَآ ءَاتَيۡتُڪُم مِّن ڪِتَـٰبٍ۬ وَحِكۡمَةٍ۬ ثُمَّ جَآءَڪُمۡ رَسُولٌ۬ مُّصَدِّقٌ۬ لِّمَا مَعَكُمۡ لَتُؤۡمِنُنَّ بِهِۦ وَلَتَنصُرُنَّهُ – Take whatever I gave you from the Book and Hikmah (understanding of the Laws of Allah, etc.), and afterwards there will come to you a Messenger (Muhammad) confirming what is with you; you must, then, believe in him and help him]. [Surah Aal Imraan. Aayah 81]
Allaah [The Exaalted] said:
قُلۡ ءَامَنَّا بِٱللَّهِ وَمَآ أُنزِلَ عَلَيۡنَا وَمَآ أُنزِلَ عَلَىٰٓ إِبۡرَٲهِيمَ وَإِسۡمَـٰعِيلَ وَإِسۡحَـٰقَ وَيَعۡقُوبَ وَٱلۡأَسۡبَاطِ وَمَآ أُوتِىَ مُوسَىٰ وَعِيسَىٰ وَٱلنَّبِيُّونَ مِن رَّبِّهِمۡ لَا نُفَرِّقُ بَيۡنَ أَحَدٍ۬ مِّنۡهُمۡ وَنَحۡنُ لَهُ ۥ مُسۡلِمُونَ
Say (O Muhammad): “We believe in Allah and in what has been sent down to us, and what was sent down to Ibrahim (Abraham), Isma’il (Ishmael), Ishaque (Isaac), Ya’qub (Jacob) and Al-Asbat [the twelve sons of Ya’qub (Jacob)] and what was given to Musa (Moses), ‘Iesa (Jesus) and the Prophets from their Lord. We make no distinction between one another among them and to Him (Allah) we have submitted (in Islam)”; then Allaah [The Exalted] said: [ وَمَن يَبۡتَغِ غَيۡرَ ٱلۡإِسۡلَـٰمِ دِينً۬ا فَلَن يُقۡبَلَ مِنۡهُ وَهُوَ فِى ٱلۡأَخِرَةِ مِنَ ٱلۡخَـٰسِرِينَ- And whoever seeks a religion other than Islam, it will never be accepted of him, and in the Hereafter he will be one of the losers]. [Surah Aal Imraan. Aayaat 84-85]
A group amongst the Salaf [pious predecessors] stated that when this Aayah was revealed, some of the Jews and Christians said, “We are Muslims”, so Allaah said, [وَلِلَّهِ عَلَى ٱلنَّاسِ حِجُّ ٱلۡبَيۡتِ مَنِ ٱسۡتَطَاعَ إِلَيۡهِ سَبِيلاً۬ۚ – And Hajj (pilgrimage to Makkah) to the House (Ka’bah) is a duty that mankind owes to Allah, those who can afford the expenses (for one’s conveyance, provision and residence)]; so they said, “We will not perform Hajj”, then Allaah said, [وَمَن كَفَرَ فَإِنَّ ٱللَّهَ غَنِىٌّ عَنِ ٱلۡعَـٰلَمِينَ – and whoever disbelieves [i.e. denies Hajj (pilgrimage to Makkah), then he is a disbeliever of Allah], then Allah stands not in need of any of the ‘Alamin (mankind and jinns)]. [Surah Aal Imraan. Aayah 97]
Anyone who does not believe that it is obligated on him to perform hajj even though he has the ability, then he is a disbeliever (Ref 1) based on the consensus of the scholars just as the Qur’aan has made that very clear. The Jews and Christians do not consider Hajj to be obligated on them, so they are disbelievers. [An Excerpt from Al-Jawaabus Saheeh Liman Baddala Deen Al-Maseeh pages 200-201. Slightly paraphrased]
Finally, we repeat once again the fact that rebutting false beliefs, ideas and views does not necessitate bad behaviour, rather Muslims are commanded to behave well towards others.
To be continued InShaaAllaah
Ref 1: If a person denies that Hajj is obligatory and claims to be a Muslim, then the scholars will advise him and decide whether he deserves Takfeer or not based on his state of affairs – knowledge, understanding, doubts etc. see here regarding principles of Takfeer: http://www.salafipublications.com/sps/sp.cfm?secID=MNJ&subsecID=MNJ09&loadpage=displaysubsection.cfm