Do you know what he was saying? I don't.
I can't lip read, and the volume wasn't loud enough.
Also, I personally don't belieive he was laughing in order to calm, appease or explain anything to her.
Thinking someone has groped you sexually, then having that person laugh directly in your face, indeed is inflamatory.
If you were standing behind a woman in a crowd, minding your own business, and she suddenly turned around and accussed you of molesting her, would you laugh at her?
If you would, you're not very intelligent.
What did this man gain by laughing at this young woman? Nothing positive that I can think of.
The entire situation, besides these 2 people, was tense, The person accused did nothing to diffuse her anger, which yes, would be any rationale persons responsibilty when in a crowd of volatile people. Instead, he did something to incite her further, he laughed at her, and also appears to be joking about her to others. Although I can't hear him, that is what his body language is saying.
If I were accused of the same, I could see myself throwing my hands in the air, and stating "I didn't do that". But not the rest of it. His taunting went on for quite some time.
The man with the pepper spray had no reason to get involved. His actions (obviously) further increased the tension in an already bad situation.