「日本人なめんじゃねーよ」を英語で言うには、どう言えばいいのですか？

If I were you, I would say,"See ? do you undestand how silly you are ? F*ck off, f*cker !!"
How is it ? 　

何故同じレベルに下げなければならないのか？
サイテイ。
こんな時こそ、センスオブユーモアを使う 　

What would you say ? I don’t think Japanese have sense of humor. 　

This is the way to learn and understand English.
If you don’t know, so be it.
　

日本人なめんじゃねーよ (closest in English would be, with out using the F-word) would be = Don’t underestimate us, Japanese
or maybe something like = Japanese are a little smarter than that
or = What do you think?... Japanese are dumb???

(Or IF you want to pick a fight) SAY　IT simple and to the point= "Don’t f*ck with Japanese people"
でもこれを言ってしまったら、ケンカを覚悟した方がいいかもね

And a quick note to Philo, Japanese do have a sense of humor, just not when someone is asking a serious question. And I　think that this guy is very serious!Just Look at the question he is asking!