" Beat a dead horse"
About "beat a dead horse", I watched the TV show " grey' anatomy ",and a doctor said " I'm sorry I asked the question. It obviously made you really uncomfortable , and I guess that's my answer. There's no need to beat a dead horse."

What's the doctor really mean ?

Question

" Beat a dead horse"
About "beat a dead horse", I watched the TV show " grey' anatomy ",and a doctor said " I'm sorry I asked the question. It obviously made you really uncomfortable , and I guess that's my answer. There's no need to beat a dead horse."

What's the doctor really mean ?

Answer

To beat a dead horse is an idiom that means to keep going over the same thing over and over again especially after the issue has already been settled.

Answer

It's an idiom. It means you're trying and wasting time on something that is not going to happen, or  that has already been attempted. 
The doctor meant he shouldn't have asked the question because his partner would not answer.