You CAN NOT have an out for Interference on the OP. Is that "taking a side" enough?
You can only have an out if a runner Interferes with a fielder who is fielding a foul ball. He is not doing so.
However, I have no problem using rule 10 to rule a dead ball when a runner interferes (no capital on purpose) with a fielder on his way to field a ball that is currently over foul territory, and then ruling said ball foul even if it rolls back fair. It's obvious that this exact scenario is a hole in the rules. But I can't justify an out here, as the INT rule is explicit in its mention of "fielding a fair ball". And I can't justify a no-call here, as the runners actions have harmed the fielder and perhaps aided the offense. No out/foul ball seems the most justifiable result.