That's very UN-sportsmanlike on your part!
4 seconds sound clip from the A King in New York (1957) movie soundboard.
You can hear this line at 01:37:25 in the Blu-ray version of the movie.
Quote context
[...]
- It's a fire! Sound the alarm, quick!
- I'm sorry. I had my finger stuck in the fire hose and had to bring it.
- Committee cites this witness for contempt to Congress.
- That's very UN-sportsmanlike on your part!
- Yes, for the plane. The trunks are to go by freight.
- Remember Sir, you haven't much time if you want to visit that boy.
[...]