In China, punching or slapping someone is extremely ill-advised because under Article 234 of the Criminal Law, any act causing harm — even minor bruising — can result in up to 3 years' imprisonment if it leads to "minor injury" as defined by medical certification. If both individuals touch each other, police often treat it as "mutual assault", prosecuting everyone involved. Compensation claims can balloon if injuries are documented, so people avoid contact to prevent escalation into a legal nightmare.
Even if it is determined no injury occurred, the Public Security Administration Punishments Law covers "disturbing public order", with fines up to 500 RMB or 15 days' detention.
But spitting does not qualify under either law, so you get scenes like this when two Chinese get into an altercation.