Well, no, I don't remember, because I don't usually engage in the competitive scene.
That aside I get what you mean.
The thing about Booing a character choice in a competitive game is that... let's compare it to something like, say, Formula One or NASCAR, and then sports.
Picking the (extremely) dominant character would be like if a racer opened up their car and showed the audience that their car has, or lacks, parts that while not
illegal to have/not have, are frowned upon.
Or if a Football/Baseball/Soccer/Basketball player came up to the Mic pre-game and told the audience they were using a performance enhancing drug (one that is legal, for the sake of the argument).
You
know the audience would boo them. XD Even if the
rules say the competitor is not in the wrong.
One of the benefits of Competitive Gaming is that most of the players tools are either immediately visible (the character they use) or the same as everyone else (controllers); the players' skill notwithstanding.
Of course, I'm probably just rambling, and what I just said makes is a bad analogy. *shrug*