You have opinions about race, sex, homosexuality, class, politics, and other controversial topics. You probably only talk about them with people closest to you. Most of us won’t touch them with a ten-foot pole, knowing how one public statement can destroy a life.
We believe we don’t have that freedom. If you don’t believe you have it, you can’t do it.
How about talking about them to the media for twenty years and being loved for it. That’s freedom.
This article about Charles Barkley described him as

Off the court, where he spun quotes and welcomed controversy, Barkley was arguably the most interesting and influential athlete of his time — maybe since Ali. While others packaged themselves as though they were just another product to be hawked in America’s ever-burgeoning commodity culture, Barkley eschewed marketing for authenticity, giving rise to a whole generation of athletes.

Whether you know him or not as a basketball player, as an extemporaneous speaker, he excels. He says things others wish they could and gets away with it. If you want to lead others, that skill will help you.
You don’t have to choose to get into the controversies he does, but read what that article says about him about a period during a challenging transition:

He sounded pensive, even glum. “I’m just driving around, thinking,” he said. “This has been home for eight years. I don’t know what to expect somewhere else.” His voice, barely a whisper, made him sound vulnerable. Oh yeah, I remember thinking, he’s still in his 20s.

It was further proof that, for all his loudmouth faults, Barkley often exhibited a greater potential for growth than any other athlete on the public scene. He was always answering questions, questioning answers and — often — lapsing into introspection.

I suggest that his potential for growth isn’t independent of his speaking his mind, but rather results from it. He’s talking about Barkley as a leader who happens to play a sport, not an athlete who happens to talk a lot.
I recommend reading the article, not to learn about Barkley himself, but to see how someone who “was, by all accounts, a shy, fat kid.”
Shy and fat!—the opposite of the fields of his greatness: outspokenness and athleticism. Everyone knows how you develop athleticism. You practice (note his Sidcha):

He shot baskets every night, sometimes all night (if he could escape his grandma’s strict, watchful eye) and cultivated his leaping skills by repeatedly jumping back and forth over a 4-foot chain-link fence.

I contend he developed his outspokenness through practice too, as the article documents. You can too.
Practicing sports made him a great athlete.
Practicing speaking freely made him a leader.
You can practice too. That’s why I made the exercise to practice your authentic voice by voicing your inner monologue, which you can do in safe environments, like with friends or by yourself. If you’ve never tried it, I recommend it.
That’s how you get to say things like this: