This conversation is a prime example of why parents shouldn't talk to umpires - it generally doesn't go well and gets confusing real fast (turns into a game of who said what).
Back to the OP for a second... IIUC - it's been claimed the umpire said the batter swung on 3rd strike and the ball hit his foot, but it was still a live ball, correct? If so, why then did the coach not protest the game? Rules 5-1-1(a) and 8-1-1(d) cover the situation. Why is no one blaming the coach here? That's not a judgement call - it's a rule and can be cause for protest.
<step up on the soapbox>
I would hope before you continue to deride umpires, remember that they are no different than yourself. You obviously made a choice to not become an umpire for a reason; otherwise, you'd be out there. I find more people that would never want to be out there - they don't want to get hit by the ball, they don't want to have some leather lung telling them they know nothing, they don't have the desire or willingness to take the time to become an umpire, etc. It's very easy to complain about a play, a pitch, a rule, etc., but typecasting umpires as doing stupid crap, disrespectful of the game, non rule knowing, etc. for making mistakes isn't fair either. I would think as the game progressed you may have had a hint along the way that some missed call or missed interpretation of a rule could have an effect on the outcome. If you didn't, then you may not have been paying that close attention or maybe all those other missed calls went your way so you were happy. The last missed call didn't go your way so you get upset. The majority of umpires at HS level aren't going pro - especially if they already have gray hair! Umpires do have to take a test and class in order to become an umpire - I'm a parent and am still looking for the damn parent test and class (OK my wife took a few pregnancy tests ;-)). Doing a HS varsity game also means a few years of climbing the association ladder doing middle school and jv ball. There are certainly some associations where word of stuff like this gets back to the assignor really quickly and there are consequences. Who knows there could have been an evaluator in the stands that day too. Umpires also have bad days and bad games - it happens. You learn from it and move on. If you don't, you won't get better games. Like Matt pointed out - a lot depends on how the umpire gets those assignments and how good the association is, how they train, retrain, and work with their umpires. Missed rules are a pretty big violation, but it's not the end for your career as an umpire. However, if there isn't an association and the school directly hires some local umpire, then why not blame the school and system for allow the situation to happen? Probably just easier to blame the umpire I guess.
<jump off the soapbox and run for cover ;-)>