Homestar............
Train's been playing the game a lot longer than you have. He doesn't hate blue because he's stupid. He knows perfectly well - probably more than you do - what blue is capable of. He knows that blue is a really powerful color, in fact, that's why he hates it.
"Broken" is magic lingo for "way too powerful." Jot that down somewhere.
Train's hatred of blue is admittedly a shtick to some extent, but he boycotts the color on ethical principle. He thinks the color, with all its "No, no, no you can't do that" ruins the fun of the game, regardless of whether you're losing to it, or winning with it. And to be honest, blue-heavy control is a bit boring.
It's certainly not a bad choice for tournaments, but the point of a tournament is to win. Us casual players - note the name of this website - play for fun, and mono-blue control is not fun.
Worse, most of us play multiplayer games, and mono-blue control is usally pretty bad in multiplayer anyway. Tempo-gaining cards such as counterspells do a really good job of screwing one player over, but they don't improve your own position at all, so while you're busy chessing one player out, the other players will get ahead of you in board development. This is why most tournament players don't like multiplayer games - because they can't hide behind their exhaustive little control cards and expect to win.
