It Takes One To Know One

This phrase is used to insult someone by saying that they are the same as the other person who they are criticizing/accusing/complaining about.

这个短语常用来侮辱某人，说他们和他们批评/指责/抱怨的那个人是一样的。

Bob says that John is a hypocrite, but it takes one to know one.

鲍勃说约翰是个伪君子，但其实他也好不到哪去。

(= Bob is also a hypocrite)

鲍勃也是个伪君子

So you say that I'm a cheapskate, do you? Well, it takes one to know one!

你说我是个吝啬鬼，是不是?彼此彼此吧!