Assalamo Alaykom,
If every human on earth claim that Quran contains errors, don’t believe them.
1) Verily, We, it is We Who have sent down the Dhikr (i.e. the Qur'an) and surely, We will guard it (from corruption). (15:9)
The disbelievers recognize Islam very well but they are arrogant. They want to be the leaders (Prophets), not Mohammad.
2) Then, if they turn away, your duty (O Muhammad) is only to convey (the Message) in a clear way. They recognise the Grace of Allah, yet they deny it (by worshipping others besides Allah) and most of them are disbelievers (deny the Prophethood of Muhammad). (16:82-83)
Allah told Prophet Mohammad ONLY to convey the message in a clear way, part of the message is:
3) And the (faithful) slaves of the Most Gracious (Allah) are those who walk on the earth in humility and sedateness, and when the foolish address them (with bad words) they reply back with mild words of gentleness. (25:63)
Is it worth it to disobey Allah and earn His anger because of those evil people? There is no reason to expose them, etc. This is what Allah said in Quran:
4) Say: O disbelievers! I worship not that which ye worship; Nor worship ye that which I worship. And I shall not worship that which ye worship. Nor will ye worship that which I worship. Unto you your religion, and unto me my religion. (109:1-6)
I can assure you that if you tell them these verses, they will become very angry. But, if you fire back into them, they will cheer because they will know that they achieved their goal. Their goal is to provoke Muslims and to mock Quran.
As you see, Islam (Quran) is very simple but we need to understand it and act upon it. Then we will win by the favor of Allah. So, please hold your horses!