In this context, "voluntarily resignation" usually means "resign now, or you're fired":

https://www.nytimes.com/2006/12/23/business/23family.html

"He could have just as easily issued a statement condemning his younger self for their sexist and puerile remarks, disavowing his older views and committing himself to doing better."

He did do all of these things. It didn't matter, he was still fired. No forgiveness allowed.

"Plenty of folks have done just that, and found themselves growing and improving as people."

In my experience, making someone apologize and then firing them anyway rarely leads them to personal growth.

"There are plenty of loud politicians that, since the 1970s, have supported gay rights; Bernie comes to mind [0]."

I don't think even Sanders supported gay marriage in the 80s. The linked clip just says that being gay shouldn't be illegal.

"Indeed I'm not even seeing what's vindictive. The wages of free speech is people reading and thinking about what you say."

Reading, thinking, and responding to speech is good and healthy. "You are never allowed to earn a living, participate in commerce, or support your family for the rest of your life, regardless of what you do or how many times you apologize" is vindictiveness.