First, my comment to glock sounded hateful and for that I apologize. Secondly, my comments applied to the specific scenario as relayed by the original poster. He said that the field ump said the fielder wouldn't have got the runner anyway. 'Evidently' in the field umps 'JUDGEMENT' there was no interference with a possible play. Therefore, the play is over. No arguing judgement calls. The OP then made the comment that the plate ump didn't have the 'kauhonies' to overrule the field ump. As long as I've been umping, it still gets me going for a coach/fan to scream at me to overrule my partner. WE DON'T WORK THAT WAY. If a coach wants to come and ask me what I seen when I made a call and ask me if I care to get help from my partner, I will do so without hessitation. We may talk about the weather, but we will get together and talk. If my partner tells me he seen something totally different, I will then chose to change or not change my call. If the coach ever ran to my partner and my partner changed my call I would leave the field and he could work by himself. Coaches......NOTE TO YOU...go to the ump that made the call (nicely) and ask if he cares to get help, your case will be heard. As for the mechanics on the specific scenario, if the field ump was in B he probably moved when the ball was hit to the SS to a postion that would block the plate umps vision of 2nd base anyway. My mechanics here are to see the out at second and follow the throw to first. If in my judgement standing 15 feet from the play there's no interfernce, then there's nothing to talk about.
As for sliding or not sliding, the runner didn't have to slide, however, if he did and he didn't slide directly into the base and went to either side as to breakup the throw, then I have both runners out. If he slides directly into the base and the fielder is standing on the base and the runner knocks him on his butt (without raising he leg above the knee), then tough luck to the fielder, he was protected if he moved to either side of the base. On the other hand, if the runner was out by 6 steps and kept going and slid into the fielder standing on the base, he's ejected for malicious contact.