In the letter, the "Anger Management" star called Williams "a stone cold passion driven and (PERFECTLY) fact based journalist."
This week, Williams was placed on a six-month unpaid leave after admitting he embellished a story about his time covering the Iraq war.
Sheen is no stranger to controversial situations that culminate in a star leaving a television show, but his experience and that of Williams are not exactly the same. In 2011, Sheen lost his starring role on “Two and a Half Men” after wild behavior that included publicly insulting show creator
In his Wednesday letter, in which abundant line breaks evoke poetry, Sheen wrote that Williams is the "victim of a vile witch hunt! Erroneously 'staged' by hooligans, non coms, cowards and oligarchs, who's only desperate and hideous goal is to discredit the genius that they relied on for almost 3 decades!"
He thanked Williams for delivering the news to his family and families across the country for so many years.
"Now and forever you are a true Patriot and a Hero of mine until the day i leave this star crossed imperfect Rock we call Earth," Sheen wrote.
Sheen tweeted a link to the letter on his verified Twitter account, which has more than 11 million followers. He soon deleted the original tweet and minutes later posted an apparently identical one without explanation.
Sheen could not be reached for additional comment.