The best arguments against it is to ask what the Qur'an actually says about hadith.

Compile every such verse. The pattern of "don't do that" stands out.

Not only that, the "perfectly preserved" Quran had to have all the various manuscripts in the empire rounded up by Uthman and literally burned. Then there's the problem that the manuscripts that still exist to this day are from centuries even after what you mentioned. Just like Christianity and Judaism, Islam's main justification for its claims is "Just trust me, bro. People don't ever make mistakes or lie, right?"

First of all, why is Hadith important? The Prophetic Sunnah as conveyed in the ahadith literature is one of the sources of shari’ah and by rejecting it such people are in clear opposition to the Qur’an, yet they have the audacity to call themselves ‘People of the Qur’an’. Allah has mentioned in the Qur’an, “And whatsoever the Messenger gives you, take it, and whatsoever he forbids you, abstain from that” [Surah al-Hashr Verse 7] “We sent down to you the Remembrance (The Holy Quran) that you may explain to people what was sent down to them” [Surah al-Nahl Verse 44] The claims made by such individuals become blatantly absurd when one considers their proposition for praying or performing Hajj without the detailed descriptions conveyed in the hadith literature from the Prophet ﷺ. Without Hadith it is impossible to know how to pray salah, how to perform hajj, what nullifies salah, the sunnahs of wudu, and other fardh actions. These quranists claim that Hadith was not recorded until 250 A.H. Which is a blatant lie. In fact ahadith were recorded at the time of the Prophet (صلى الله عليه وآله وصحبه وسلم) himself. The following are by way of example: When Fathu Makkah occurred in 8 a.h. the Prophet (صلى اله عليه وآله وصحبه وسلم) stood before the people and delivered a sermon. One of those present was Sayyiduna Abu Shah (رضي الله عنه) from the people of Yemen and he requested that the words of the Prophet (صلى الله عليه وآله وصحبه وسلم) be written down for him saying: “Write it down for me O Messenger of Allah.” The Prophet (صلى الله عليه وآله وصحبه وسلم) said: “Write it down for Abu Shah.” [Sahih al-Bukhari hadith 2434] Sayyiduna Amr ibn al As (رضي الله عنه) narrates that he would write the ahadith of the Prophet (صلى الله عليه وآله وصحبه وسلم) and memorise them until some people dissuaded him from doing so and he stopped. He narrates that he mentioned this affair to the Prophet (صلى الله عليه وآله وصحبه وسلم) who told him to write, taking an oath by Allah and saying: “Nothing exits from me except that it is the Truth.” [Musnad Imam Ahmad Hadith 6510] The existence of well-known hadith compilations such as the Muwatta of Imam Malik (d.179 ah) (رضي الله عنه) pre-dating Sahih al-Bukhari also points to the shallowness of their claims. Another early example of hadith recording is found in the Tabi’i Sayyiduna Hammam ibn Munnabih (d. 131 a.h.) (رضي الله عنه) who recorded ahadith narrated to him from Sayyiduna Abu Hurayrah (رضي الله عنه) in a work known as ‘Al-Sahifah al-Sahihah’. This complete work was later related within the text of the Musnad of Imam Ahmad (رضي الله عنه). These are some basic points indicating upon the corruptness of the call to reject the ahadith books. If you want to protect your imaan then avoid contact with these heretics and innovators. Complete rejection of the ahadith literature which encompasses mutawatir (mass-narrated) ahadith which benefit qat’i (conclusive, definite) knowledge is an act of clear kufr and will take you out of fold of Islam. May Allah ‎عزوجل protect our imaan.

Politics. Sunni’ism had always been a compromise with the Ummayads and Abbasids. This is not an academic response by any means, so I urge you to look at Joshua Little’s work on isnad based Hadith system. In fact he specifically picked on the controversial Hadiths about Ayesha. His conclusions are, well, interesting to say the least.