Peace Savage_Carrot,
The problem is that you guys have really widened the meaning of kufr when the Quran has only talked about it when it comes down to covering the truth about Allah as far as I know
"Who then is more wicked than one who lies about God, and denies the truth when it comes to him? Is there not in Hell an abode for the rejecters? (3932)
"His friend said to him while discussing with him "Have you disbelieved in the One who created you from dirt, then from a seed, then He evolved you into a man?" (1837)
"We did not create the heavens and the Earth, and everything between them except with truth, and for an appointed time. And those who disbelieve turn away from what they are being warned with." (463)
"Rejecters indeed are those who have said "God is the Messiah the son of Mary." Say "Who has any power against God if He had wanted to destroy the Messiah son of Mary, and his mother, and all who are on Earth!" And to God is the sovereignty of heavens and Earth and all that is in-between; He creates what He pleases. God is capable of all things." (517)
"Those to whom We have given the Scripture, they recite it as it truthfully deserves to be recited; they believe in it. As for those who disbelieve in it, they are the losers." (2121)
"And they serve besides God what does not benefit them nor harm them. And the rejecter is always set-against his Lord." (2555)
"And from among the people of the Scripture are those whom if you entrust him with a large amount he gives it back to you, and there are those whom if you entrust with one gold coin he will not return it to you unless you are standing over him. That is because they said "We have no obligation towards the Gentiles." They say about God lies while knowing." (375)
"And it has been sent down to you in the Scripture, that if you hear God's revelations being rejected and ridiculed in, then do not sit with them until they move on to a different subject; if not, then you are like them. God will gather the hypocrites and the disbelievers in Hell all together." (4140)
"And from amongst them is a group that twist their tongues with the Scripture so that you may think it is from the Scripture, while it is not from the Scripture, and they say it is from God while it is not from God, and they say about God lies while they know." (37
"And from the camels two, and from the cattle two. Say "Is it the two males that He forbade or the two females, or what the womb of the two females bore? Or were you witnesses when God ordered you with this?" Who is more wicked than one who invents lies about God to misguide the people without knowledge. God does not guide the wicked people." (6144)
"Who is more wicked than one who invents lies about God, or denies His revelations? These will receive their recompense from the record; so that when Our messengers come to terminate their lives, they will say "Where are those whom you used to call on besides God?" they said "They have abandoned us!" and they bore witness upon themselves that they were rejecters." (737)
"Who then is more wicked than one who lies about God, and denies the truth when it comes to him? Is there not in Hell an abode for the rejecters?" (3932)
From what I understand these verses all point to how kufr refers to covering the truth about Allah. Some of these examples include false religious teaching that made up rules and say it was from Allah, disbelieving in Allah, change the meaning of verses, telling lies about Allah. I have not seen an example as far as i've seen that refers to anything that isn't related to covering the truth about Allah. I haven't seen any evidence in the Quran as far as i've seen that points to Kufr having a wider meaning.
Someone lying that they didn't cheat in a math test while they did? I don't see them referring to Allah at all here, let alone any sort of religious reference whatsoever. They are lying about their actions instead without any reference to Allah. The Quran as far as i've seen refers to kufr in regards to covering the truth about Allah.