You made some very serious accusations against your former employer, and I hope they will be examined and acted upon accordingly. It sounds as though you were successful there while dealing with some tough personal challenges.
Personally, I don't think one tweet makes anyone a racist or any of the myriad of other unjustified names, people who know nothing more about you than this article, have called you. I’m quite sick of the cancel-culture on both sides. That doesn't mean you didn't tweet a racist comment, it just means one tweet does not define you.
You stated that there is always a threat tweets that challenge white supremacy will be weaponized. Your tweet did not challenge white supremacy. It was a comment from a reporter, a person in a position of trust, a person whose job it is to ensure inclusion (and as I understand it, inclusion means everyone, not just a select few); a reporter who did not check her facts, have any data or research to support her claim, made no attempt to determine the truth, or to clarify that the claim was her own personal opinion.
You broke the #1 rule of good journalism. You need to own that.
No, your tweet does not, in and of itself make you a racist. Nor do I think anyone should be fired for one tweet alone. We do have freedom of speech in this country. But your tweet did show poor judgment and is an example of bad reporting. Both of which are fixable with work and self reflection.