Updated on 2018-06-09: That law was originally passed because of a particularly nasty desease that spread via saliva … (it’s a theory, at least).

↓ Transcript
Halen: Sweetie, don't you think you're being a bit unfair? It's what they do to survive. They might not have a real alternative ... Just ... don't judge them too harshly, hm?
Katharina: <mumbling> I'm not ... JUDGING.
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Katharina: But why ... you know ... TOGETHER? They could work SEPERATELY ... it just made me ... EXTREMELY UNCOMFORTABLE.
Halen: Maybe they get more clients that way.
Katharina: But ... BROTHERS! Who'd have a thing for THAT?
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Halen: <grins> Well from what you're telling me ... SHARA.
Katharina: Great, now I'm picturing them ...
Halen: Maybe it'll help you if you focus on something ELSE ... and tell me which belt I should choose?
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Katharina: But isn't Prostitution ILLEGAL here?
Halen: No, why would it be?
Katharina: Well ... it was in Beckstown ...
Halen: <sighs> Yes, darling. So was KISSING IN PUBLIC. It was such a PRUDISH city ...