Let me clarify: for a state of fascism to exist, Batman would have had to actively suppress all opposition, disagreement, and criticism of his ideals and set himself up as the sole voice that matters in the entire establishment. A dictatorship, if you will. Which, obviously, never happened. The JLA situation simply doesn't work like that; Batman never ascribed to all power or wanted it. He kept his own ideas relatively unsaid because he knew no one would agree with him, and he didn't want them to agree with him because it was a personal fear, not something he felt that everyone should believe in. In an organization like the JLA, people like Superman and Green Lantern would always, always have some measure of power simply because they were powerful people; in this sense the JLA would never become anything more than a democracy due to its checks and balances. Did Batman want a measure of control over that? Of course. But a measure of control is not total control, and is therefore not fascism. He never once said, "No Wally, you can't do this because I said so." He always said, "No Wally, you can't do this because if you do, we're all fcked."
Batman had a suspicion of metahumans and those with more power than ordinary humans should have. Therefore he felt that he needed some power for himself, and he relied on fear and intimidation to do so. That is posturing. It's like a cornered cat raising the hair on its back to look larger. It's not the mark of a dictatorship in which all other opposition would be silenced.
And guess what? HIS FEARS WERE FOUNDED! Max Lord did control Superman, Luthor did control Superboy, and the secret Leaguers did abuse their power and mindwipe him and others like him, which eventually led to old problems coming back to bite them in the ass! I don't agree with Batman's issues and the way he went about it, but it was far from the active oppression that actually constitutes fascism.