"It makes you wonder why they think they can argue/reason their way out of it."
Because the same mindset which impels one to make videos about cheating or replying to cheating accusations with videos makes it impossible for the child or manchild to consider their actions.
The manner of speech from the one guy who talks shows an inability to properly compose natural language.
These types of people operate entirely on instinct, and lack introspection and reason.
They feel wronged, and so lash out by impulse.
If any are in their teens or early 20s it's because they are physiologically incapable of consideration even if they were inclined to try: the frontal lobe, which is responsible for reason, introspection, and planning, isn't fully functional in males until they're in their mid-20s. If they are older than that, it's because they're a manchild. Like the Bamster, vegetarians, or people who think humans are capable of living in peace.