Obstruction??

[oppool]

B1 gets a hit to deep center and is obstructed by F3 while making the turn at first. You rule obstruction at this time and figure your protection will go to 3rd but the ball is slow coming in and the runner is faster than thought. The runner is put out sliding into home. Your ruling??

This play was discussed this weekend in our metro clinic and I didnt agree with the answer that was given as correct. So I brought it here for discussion

Thanks

Don