In that instance, it is not rude to ask, because you are not allowed to show one and not show the whole table. I learned that the hard way because I was playing a live cash game and there was this guy who played almost every hand and was winning big pots while losing small ones. This is at 1.2 and I have about 150 in front of me while he had about 400 in front of him. I finally decided to make a stand playing a hand and I had garbage, and bet every street, well it worked out and the guy sitting next to me was like holy crap you must have the stone cold nuts when I made my river bet, and the guy tanked for about 2 minutes and folded. Showed the person, and then mucked but the player asked to see my cards and I had to show, everyone got to see my play, and I was not happy. It could have lead to much more money for me.