Who cares if someone tells a lie? Well, it depends on who you ask.
If you ask someone who’s used to lying a lot himself, he would say we’d have to be tolerant to people who tell a lie once in a while.
Someone who hates to tell lies, on the other hand, would say it’s kind of a crime to tell lies, and that some kind of punishment is therefore justified in order to drive back the tendency of telling lies in our communities, as he knows it would break trust between friends, and ultimately break trust between people and people groups all over the world.
This, of course, is maybe a bit of a simple black-and-white example, but at least it gives us a feel for how sinning in general would and should be judged.
God lives in a world where there are NO LIES!! And so, He won’t accept us in that world if we’re okay with being liars, or other types of sinners—unless we sincerely repent of our sins, and try to live according to the righteousness of God—through the forgiveness of sins which came available to us humans with the sacrifice of Jesus Christ on the cross of Calvary.
A few examples of how bad our sinning is before God
Just to get a feel for how bad our sinning is in the eyes of God.
The Bible says that you’re a murderer if you hate your brother.1
And that God doesn’t forgive you when you cannot forgive another human being from the heart, causing you to go to hell at the end of your earthly life.2
And even if you merely call someone an idiot or a fool, you will be worthy of hell.3 (Note also that in the same verse it says that you’re even guilty when you continue to be angry with your brother or harbor malice against him.4)
And if you look with lust at another person who’s not your spouse, you have already committed adultery with that person in your heart.5
See also Galatians 5 (vs 16-24) for a list of things we are not to do (vs 19-21), and for things we should actually strive for (vs 22-23).
2. Matthew 18:35 and Matthew 6:14-15
3. Matthew 5:22
4. idem (Especially, take note of the Amplified Bible text)