A-Rod defends controversial shout. Time to quote the rulebook. 7.08 (b). Any runner is out when — He intentionally interferes with a thrown ball; or hinders a fielder attempting to make a play on a batted ball;

Rule 7.08(b) Comment: A runner who is adjudged to have hindered a fielder who is attempting to make a play on a batted ball is out whether it was intentional or not.
If, however, the runner has contact with a legally occupied base when he hinders the fielder, he shall not be called out unless, in the umpire’s judgment, such hindrance, whether it occurs on fair or foul territory, is intentional. If the umpire declares the hindrance intentional, the following penalty shall apply: With less than two out, the umpire shall declare both the runner and batter out. With two out, the umpire shall declare the batter out.