What was the argument about?
I couldn't understand one word!
Pretty sure nothing important, I'm pretty confident that the girls started it. Usually in these train arguments, if it was something like sexual harassment, they'd have more dudes and women sticking up for them. Also, the girls themselves would've had a different tone to them.
My guess is that they either were goofing on his fashion sense and he said something or he lightly flirted, and they started goofing on them. Of course, the old "you stepped on my toe", "your bag bumped me", or "you smell" are always classics for these things.