Interference at first base

[RustyWinslow]

My fault........bad choice of words. The play was not "overuled", the interference call was just........"enforced????" (and, to his credit, in a quick and timely manner). As I said before, there was no argument to the call, just wanted to clarify the rule. Ask a question about one rule.......learn something new about another. I would have continued to think that an umpire stepping in and calling interference on his partners call would be breaking the old unwritten rule of "don't show up your counterpart".
However........I still need some help on my earlier comment:
"Technically first base is "to the left" of the inside foul line. How does this apply to 7.09 (k) and when is the runner entitled to run directly to the bag....blah, blah.... at some point BR has to take a path inside the foul line in order to hit the bag."
In terms even I can understand........."if the F1 is directly on top of the bag (and I mean directly with both feet), in the process of fielding the throw and BR runs in to him (without malicious intent, purely agreeably coincedental).....is this interference.
Let me guess.........the dreaded, unarguable JUDGEMENT call. I don't argue those, looking for something cut and dry....and I'm not gonna get it am I?
thanks again for all the help