Interference with ejection ?

[tankmjg24]

10U USSSA game and I am the field umpire. R1 and BR hits a ground ball to F6 who throws to F4 to begin the attempt at a double play. R1 is out by about 20 feet give or take. F4 comes across 2nd in the direction of 3rd and begins to throw to F3 but double clutches then throws wide into the dugout. R1 went into second standing up, but he ducked his head and veered inwards. I signaled the out at second then called BR out for interference by R1.

The manager who is the first base coach comes out and wants an explanation. His statement to me is that the runner does not have to slide. My response was that I agree, however he cannot veer into the path of the throw as this is interference. He replies by saying that I am wrong and that the runner can do whatever he wishes and that he wants to appeal to the plate umpire. I deny his appeal and tell him that the out stands and we are going to play ball. He kind of stands there for a second then replies with the comment that if I am going to umpire this level of ball he wishes that I would learn the rules. He then brings up a previous play where he thought a balk had occurred. At this point he turns to walk back to the coaches box and drops a "bullsh*t" under his breath but loud enough that I could hear him. This is where I ejected him. He argued a bit more but eventually simmered down and left the park.