I was playing on clay in a friendly doubles game last week against a couple of older ladies that are on my team. One of them has a habit of calling very close balls out, and I know that before we even start - but they took three points in one set on balls that I definitely thought were in (not balls at the baseline, but down the line shots that I had a clear view of). I didn't say anything about the first two, but on the third one, which I believed was a clean winner - I said, "are you sure?" "Can you show me a mark?" She circled the mark, and it was right on the outside edge of the line. The mark was a half-moon, not a full circle, nestled right against the line - and part of the line was clean. She still insisted the ball had been out, and in fact threw a temper tantrum, throwing her racquet up in the air and saying, "what - are you calling me a liar?!" I said just relax, take the point, we'll forget about it. A couple of points later she called my ace serve wide, when it clearly zinged off the center tee. I said, "oh - that was out?" And she went ballistic again. Actually I was just looking for confirmation - I wasn't sure that she'd called out - and it was just unbelievable that she did... Later I apologized, and assured her that I was not calling her a liar! My question here is - when someone questions your call, do you automatically think they're calling you a liar? Should we always just clam up and "take our medicine" even when we think our opponent is making terrible calls (especially in a friendly game)? I thought that according to the Rules, we could politely ask to see a mark, particularly on clay. This "are you sure" question doesn't mean "you're a liar/cheater" but it seems to always be taken that way.