Ace, it might not be our job to "explain" calls, but I think if the defensive coach comes out in an appropriate manner and just talks with me, he can get his explanation.
If he starts the yelling screaming "terrible umpiring" antics, then he no doubt is getting one word answers.
Something I learned several weekends ago at a clinic for basketball that I think holds true for baseball.
1) Answer questions. Don't respond to statements.
2) Allow coaches to speak, and acknowledge that you are listening. Sometimes they just need somebody to talk to.
3) Remember that, in his eyes, your calls will either help or hurt him from winning, and his job depends on winning. So its natural for him to get upset... even when you're 100% right.
4) Use positive communication with the coach, don't use "don't" statements.
Two weeks ago I was calling a U15 game. Pitcher double sets, I balk him, here comes HC. Starts yelling at me from the foul line. I respond "Coach, you can come here and talk". He comes out and as he was approaching I said again, "just talk Coach. I'll listen".
He went on about how his pitcher never balks, how this time was no different, on and on and on for about 10 seconds, in a conversational tone of voice. I just stood there, hands at my side. He then finally asked, "what did he do?" I gave him his answer, "double set", and he said back, "well I don't think he did" and turned to get back to his dugout.
Just by telling him to come talk when he was yelling from the foul line, and acknowledging that I would listen to him, I didn't have to dump this guy. Also responding to his statements would have just gotten him riled up, but when the time came, I answered his question.
This whole incident took maybe 30 seconds, but I gave the coach positive communication, allowed him to speak, made it look like I cared what he had to say (I could really give two rats a$$
) I think an approach similar to this would have worked well in the OP sitch.
Thoughts?