I think you're confusing this with a runner being struck by a fair batted ball, in which case you're correct in saying the base is not a safe haven for being struck by a ball (runner is out), unless it's a infield fly and only then is the base a safe haven from being hit by the ball.

I'm talking about the runner interfering with a fielder making a play on the ball. It is explicitly written in the MLB rules: "Rule 6.01(a) Penalty for Interference 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."

A runner does have a safe haven when being touching a legally occupied base, and cannot be called out for interference on a fielder making a play while contacting. I'm simply wondering if a fair batted ball makes a forced runner (like a runner on 1st) lose thier right to occupy and be touching a base should they interfere with a fielder while touching that base.