The only way every team could have exactly the same chance of winning is if all 64 teams were exactly the same teams, coaches, and players, playing games at exactly the same locations against the exact same opponents. All the variables would have to be exactly the same.
Are any of those claiming every team has the same chance of winning willing to put their money where their mouth is? I bet you $10,000,000 that a majority of the #1 seeded teams will win in the first round. If a majority of the #16 teams win, you win. If neither group wins a majority of the games, nobody wins (which is fairly likely since, according to you guys, the chance of each of these teams winning is exactly the same). Any takers?