I guess my point is this, a runner can easily "kick" a ball without necessarily doing anything obvious that makes it an easy call of "intentional".
When I say that the batter-runner "kicks" the ball, many of you are probably envisioning the runner breaking stride and taking a swipe at the ball with his foot. Yes, that would
clearly be intentional. No brainer.
I'm not talking about winding up like a soccer player taking a penalty kick. Of course that would be an easy ruling of "intentional".
Since a natural running motion necessarily involves rapidly placing one foot in front of the other - a runner could
easily convert that running motion into a "kick" without even breaking stride. It could look
completely natural and unintentional when, in fact, it was completely intentional.
Therefore, I'm thinking that for the purpose of standardization and consistency, if a runner "kicks" a foul ball that has the potential to be fair - the runner is OUT because all "kicks" are deemed intentional - by interpretation. And, as Dave Reed pointed out, this would be particularly true in situations where the ball has rolled up the line some distance where the batter had a reasonable amount of time to avoid the ball - even if the runner did not seem to do anything intentional. The fact that he did not avoid the ball and "accidentally" kicked it is considered intention enough no matter how "unintentional" it may have
appeared.
(Thinking out loud mode) No reading of the mind is necessary. That ball had the potential to be fair and you kicked it. It doesn't matter how it
looked.
You're out! You had a choice to run around the ball or step over it and you
chose to do neither.
Just to complicate things ...
Let's say the runner does something that seems to be a clear attempt to
avoid the ball. For instance, like attempting to jump over it and, in the process, he ends up "kicking" it. (How's this for beating a dead horse?)