Yes, I think that is too tin foil hat.
Its sound much more likely that you've got some poor coaches, whose bad behavior was actually embolden by some of your actions. As others have mentioned, you let way too much go, and let it go on far too long, but I suspect there were things in your actions that also encouraged their bad behavior.
You are talking about 10U ball, where the pitchers have so little control that you've been told to call the opposite batters box a strike - and yet you think the pitcher has enough control to intentionally throw at your head? Doesn't it seem more likely that the pitcher asked the catcher to move out because, as you've made clear, that was part of your zone and then lost control because he's a 10 year old pitcher?
I'm not saying it's not possible for a pitcher to intentionally try to throw at you - but when that's your first instinct, in 10 year old ball, where the catcher did make an effort to catch it, I read it as you were already treating everything like a potential confrontation and players and coaches can see that in you too, which is likely to increase problems.
This to me is the cardinal sin. Rather than shutting down poor sportsmanship by coaches and players, you actually escalated the situation here and only encouraged more bad behavior, by engaging in bad behavior yourself.
I understand getting frustrated, but that's all the more reason to shut down bad behavior and shut it down quickly.
This also I think is a big part of your problem - you issued a warning, and then when the behavior continues, you didn't follow through, thus undermining your own credibility. The warning didn't mean anything because they didn't think you would follow through - and you didn't.
It's not really a surprise that once you actually did take action, things improved significantly. Learn from that. It's not fun to eject someone from a 10U game - but it's still a whole lot better than teaching kids horrible sportsmanship, which as you saw yourself, they will quickly start copying and acting out themselves if they think it's acceptable.
