Balk's

At a game last night my son's team was called for four balks. Two on the pitcher for taking signs off the rubber and two on the FIRST BASEMEN for having a portion of his body in foul territory (his feet while straddling the bag).

Now I know baseball rules state that you must take the sign from the rubber, but the rule was intended to prevent quick pitches (these were obviously not quick pitch attempts) the rules don't specify that doing this result in a balk call. as for the first basemen, I have never heard of a balk being called on anyone but the pitcher. The umpire told us that no part of a player can be in foul territory (except the catcher) while the pitcher is on the rubber. We argued to no avail. Even the opposing coaches agreed with us. Has anyone ever heard of such a thing? Any comments or clarifications on this rule?