I can suggest you what you can do.

You can walk up to him, stare at him, and say, not loud, only for him: Sir, I couldn't tell what you just said since apparently you intended it to yourself, but from that word I happened to have overheard, it was not a friendly one. And I think you look like a "Chinaman" too since you look like a human being. Are you not a human being?

The above is only a suggestion. If you think reporting someone's private murmuring is more effective, then you can try it too.

所有跟帖： 

• 就你聽到了，你還啥都沒做 ，他咋“輕則挨批，重則丟飯碗”？，反駁無力、 -未完的歌- ♂ (0 bytes) () 02/02/2023 postreply 11:36:26

• 小謝，自欺欺人的恐怕是你自己。如果我碰到，我一定讓警察跟他（她）交流一番。你也好意思，當場一聲不吭，事後跟同胞抱怨。抱怨 -馮墟- ♂ (141 bytes) () 02/02/2023 postreply 11:40:25

• 說實話，這事如果發生在室外，我很可能不喊警察自己當場搞定。 -馮墟- ♂ (0 bytes) () 02/02/2023 postreply 11:42:38

• 你會遇到的，希望你的智慧和果斷不衹停留在中文論壇上。 -中間小謝- ♂ (60 bytes) () 02/02/2023 postreply 11:52:20

• 你以為我生活在真空中呀，就你這能耐，還教訓別人。你怎麽知道，你的希望不是我的現實？ -馮墟- ♂ (0 bytes) () 02/02/2023 postreply 11:55:28

• OK, tell me about it. -中間小謝- ♂ (158 bytes) () 02/02/2023 postreply 12:19:20

• Stop the person, have a conversation, ask him what he said -馮墟- ♂ (931 bytes) () 02/02/2023 postreply 12:35:07

• This is a very very weak case, -中間小謝- ♂ (1458 bytes) () 02/02/2023 postreply 12:58:13

• the "problem" is no adult ever uttered "chinaxxn" -馮墟- ♂ (131 bytes) () 02/02/2023 postreply 13:03:39

• 小謝，別跟我費工夫了。影雲勸你回中國，美國好危險，這對你可能是一條正途。 -馮墟- ♂ (0 bytes) () 02/02/2023 postreply 13:09:12