Why when you call people out for certain things they flip things and make out you are in the wrong?

So this guy I was seeing, I called him out for him accusing me of cheating on him when I never cheated and he lied and said he never accused me, even though the proof is in the message he sent. Instead off apologising, he flipped things and said i was a trigger and he was feeling suicidal. I would call him out for lying and he would get defensive and say he has never lied. I called him out for lying about his parents disowning him, when he started to threaten to commit suicide and when I said I was going to call the cops to get them to check on him, he then threatened to call the cops on me before blocking me.

Why when you call people out for certain things they flip things and make out you are in the wrong?
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