It's common when people are lying that they get defensive or they start acting calm, and failing at it.
"You're lying"
Defensive:
"No I'm not, you jackass!"
"And I'm sure you've never lied before"
"Because nobody can have a life outside of the forums"
"It doesn't matter what you think"
Acting Calm and fake jokes:
"If I was lying, it would show! I am a very bad liar!"
"Would I lie?"
"Let's base that I'm lying lol"
"OH NO YOU CAUGHT ME[/sarcasm]"
"You're right! I have no life and I'm a lie!"