Wow. Some of you can only be described as bullies.
I have no idea what the original post said. I don't know if the DPE was mocking the applicant, or simply flustering him by him repeat himself, or asking him to explain an idiom that the OP had no idea what it meant because he wasn't a native English speaker. Either way, if the OP was going for a CFI ride, ability to communicate extremely well in English is terribly, terribly important, for reasons I'm sure everyone knows.
However, the OP has repeatedly wondered if "it's illegal to be rude" and seems a bit bent out of shape over the DPE's perceived and alleged rudeness. I don't know why calling out that attitude would be considered "bullying". Freedom of speech is still relatively protected here, and rudeness is often subjective. I've had people say things that could be considered rude or offensive to me about my Minnesotan accent, and I barely have an accent most of the time, so if he has an accent, I think he can count on students and ATC commenting sometimes on that accent. If the DPE's manner/comments about his accent are enough to rattle him so he can't satisfactorily complete the checkride, it's a legitimate concern to raise about his ability to handle an in-flight situation of the sort. If he is flying into an uncontrolled airport and asks the other plane in the pattern on base what he is doing, and the pilot responds he is "about to call it a day", is OP going to get bent out of shape again because he doesn't understand that idiom and everyone just expects him to know what is meant? (And I know that's not standard phraseology, but pilots don't always talk in standard phraseology.) What if he is a CFI and a student can't understand him? Is the student allowed to say, "Your accent is making it impossible for me to understand you" or is that rude?
I think that people are jumping on him because he is being overly sensitive in reaction to this. I know it stings to have failed a test, but unless the DPE based OP's failure entirely on his inability to understand idiomatic English, which I highly doubt, OP is simply looking for a way to justify his failure and pass off the responsibility for it to someone else, which goes directly against the need to own up and take responsibility for everything he does if he wants to be successful in the world of aviation.