There's nothing worse than a sore loser. Half the trick to being a good sportsman is, should you be losing or should you lose, you do it with grace. As a kid, I played tennis all the time. There were players better than me and ones worse than me. By far the players I disliked the most were those who just could not and would not be graceful even in defeat.
You don't have to like losing but you sure don't have to be an ass to the winner about it.
Why am I writing this brief entry? I'd rather not say. Suffice that the entry itself says plenty.