Had a situation in a men's adult rec league last evening.
Runner on first one out. Batter hits a line drive to left field. Runner on first rounds second and is going to third.

Runner arrives a fraction before the ball and slides into third and is safe. The ball hits the runner on the knee while he is sliding and is deflected by the third basemen and the pitcher who is backing up the play. The ball rolls slowly out of play. I rule over throw and award runner home but the pitcher argues because the ball was deflected by the sliding runner.

Please help. Thanks

Good call. Tell the pitcher you cannot control the wild arm of the left fielder. Maybe if he threw the ball to his teammate instead of at the runner it wouldn't have gone out of play. :)

For the newbie:
Merely tell whoever is arguing that it would only make a difference if the runner contacted the ball intentionally and you clearly saw it wasn't.