How would you respond to a Quranist or hadith denier?

The issue surrounds whether the Messenger (saw) received Qur'an only or additional revelation. Quranists believe the Qur'an itself is sufficient and all ahadith are to be rejected. Some verses cited to support this position are 45:6, 6:114, 10:35, 6:19, 10:15, 25:31, 39:23. Obedience to the Messenger (saw) is then limited to what appears in the Qur'an for them. The question is then, did the Messenger (saw) receive revelation in addition to the Qur'an? The Qur'an answers in the affirmative. Here are some examples: 1. Change of Qibla In the following verse the Messenger (saw) was following a previous qibla established by Allah, but where is the command in the Qur'an for the Messenger to follow this first qibla? “Thus We made you a moderate community, that you may be witnesses to humanity, and that the Messenger may be a witness to you. We only established the direction of prayer, which you once followed, that We may distinguish those who follow the Messenger from those who turn on their heels. It is indeed difficult, except for those whom Allah has guided. But Allah would never let your faith go to waste. God is Kind towards the people, Merciful.” (Qur'an 2:143) It does not exist. We can only conclude the Messenger (saw) received revelation apart from the Qur'an. 2. Knowledge of support of Angels A second example is: “Allah had given you victory at Badr, when you were weak. So fear Allah, that you may be thankful. When you said to the believers, “Is it not enough for you that your Lord has reinforced you with three thousand angels, sent down?” It is; but if you persevere and remain cautious, and they attack you suddenly, your Lord will reinforce you with five thousand angels, well trained. Allah made it but a message of hope for you, and to reassure your hearts thereby. Victory comes only from Allah the Almighty, the Wise.” (Qur'an 3:123-126) How did the Messenger (saw) know Allah would support the believers in the battle with angels? There is no verse in the Quran where Allah states this. Additional revelation is the only explanation. 3. Marriage to Zaynab There is the example of the Prophet (saw) marrying the companion Zayd’s ex-wife: “When you said to him whom Allah had blessed, and you had favored, “Keep your wife to yourself, and fear Allah.” But you hid within yourself what Allah was to reveal. And you feared the people, but it was Allah you were supposed to fear. Then, when Zayd ended his relationship with her, We gave her to you in marriage, that there may be no restriction for believers regarding the wives of their adopted sons, when their relationship has ended. The command of Allah was fulfilled.” (Qur’an 33:37) The verse says, “You hid within yourself what Allah was to reveal and you feared the people, but it was Allah you were supposed to fear.” Why would Allah address the Prophet about this if he didn’t know he would eventually marry Zayd’s wife? If someone is hiding something they must have knowledge of it. Again, we can only conclude Allah informed him Zayd would divorce his wife and he would marry her. Conclusion Obedience to the Messenger (saw) is not limited to the Qur'an. The Quranist position is false as it limits revelation to the Qur'an, which is a contradiction with the Qur'an itself. This can be formulated as a deductive argument: If the Messenger (saw) received revelation apart from the Qur'an, then the Qur'an only position is false. The Messenger (saw) received revelation apart from the Qur’an (2:143, 3:123-126, 8:9-10, 33:37, 66:3 etc). Therefore, the Quranist position is false.