The One With The Tea Leaves - S8-E17
Mona: Ross! What are you doing?
Ross: Not touching myself, if that makes anyone less uncomfortable.
The One With The Nap Partners - S7-E6
Rachel: Hi! I just want to apologize. I'm really sorry I was a baby.
Phoebe: That's ridiculous Rachel, we were all babies once.
Answer: The statements that she's contradicting (that it is common, it happens to every guy, and it's not a big deal), are the things that a woman commonly says to a man who is suffering from erectile difficulty, typically to assuage his bruised ego. However, most men do not believe that these statements are true, as evidenced by Chandler's outburst. He's so caught up in the proof that women are lying about it that he gives himself away.
Rooster of Doom