The oneness of God!
This hate is because of the lack of knowledge.
Hindu’s ‘Nirakar Brahman’ & Muslim’s ‘Allah’ are not 2 different beings but one true supreme being we know by different names. Hindus call him Ishwar, Muslims call him Allah, Christians - Jesus & so on.
Say: O People of the Scripture! Come to a common word between us and you: that we shall worship none but God, and that we shall ascribe no partner unto Him, and that none of us shall take others for lords beside God. And if they turn away, then say: Bear witness that we are they who have surrendered (unto Him). [3:64]
The oneness of God is mentioned in every true religious scripture.
In the Qur’an:
Say, "He is Allah, [who is] One, [112:1]
In the Atharva Veda:
Only he is One, who by Himself (without being born to anyone) alone is present [13:4:12]
In the Bible:
The most important one,” answered Jesus, “is this: ‘Hear, O Israel: The Lord our God, the Lord is one [Mark 12:29]
So let us try to learn as much as we can & unite under common name for the one true God. You can call him whatever you want but he is only One.