[MD Longhorn]

Manny, I think you're missing the boat here quite drastically.

If the fielder is near a base when she obstructs a runner, it is COMPLETELY common for that obstruction to have affected that runner both before and after the base. If you do not rule this way, you're really creating a situation where it's advantageous for a fielder to simply get in the way most of the time. If you're ruling this way, and your my umpire, I'm stationing my first baseman directly in front of the bag on all hits that are in between single/double ... pretty much ensuring they just get a single.

Or worse, my third baseman is going to stand in front of third and push the runner toward home such that they miss third base on any borderline scoring play. You'll only protect them to third unless you're sure they would score, so I'm gaining by obstructing.

Yes, we protect them (and award) those bases that we feel they would have achieved had there been no obstruction ... but the other half of that is just as important. If a fielder obstructs near first - and that obstruction affects the runner AFTER first, they are protected between first and second as well, even if the umpire doesn't think they'd have gotten to 2nd.