Tillerson made one of his first public speeches since his ouster in March as he spoke to graduating cadets from the Virginia Military Institute.
In remarks to graduates of the Virginia Military Institute today, Tillerson lamented assaults on facts that he said would lead to a loss of freedom.
Tillerson said the damage done by a lack of public trust in certain individuals and institutions at the top, disturbs the concept of a free society.
"It is also that foundational commitment to truth and facts that binds us to other like-minded democratic nations - that we Americans will always deal with them from the same set of truths and facts", he said.
Trump fired Tillerson by tweet in mid-March, later explaining that he didn't see eye-to-eye with him.
"A responsibility of every American citizen to each other is to preserve and protect our freedom by recognizing what truth is and is not, what a fact is and is not, and begin by holding ourselves accountable to truthfulness, and demand our pursuit of America's future be fact-based".More news: Alberta passes legislation to cut off oil supply to BC
"If our leaders seek to hide the truth, or we as people become accepting of alternative realities that are no longer grounded in facts, then we as America citizens are on a pathway to relinquishing our freedom".
Many took Tillerson's comments as a thinly-veiled rebuke of Trump, who's often criticized what he terms "fake news". In just a few weeks on the job, Pompeo has already reversed two heavily criticized Tillerson directives, ending a 16-month hiring freeze and reinstating a program that offers employment opportunities for the spouses of diplomats posted overseas. Tensions seemed to mount over disagreements on how to handle the threat of nuclear proliferation in North Korea and Iran. If not addressed, "American democracy, as we know it, is entering its twilight years", he said.
Tillerson's most powerful theme, however, was the importance of standing up for the truth.More news: Ebola outbreak in the Congo spreads to major city, health officials confirm
Since his firing, Tillerson has spent much of his time at his ranch in Texas, according to The New York Times. "Look for employers who set high standards for personal conduct and who reward ethical leadership", and emphasized that integrity is the most valuable asset they have. His tenure as secretary of state was criticised for his perceived aloofness, his failure to fill rank-and-file jobs and his failure to maintain the alliances he touted in his speech.
Mr Tillerson, a Texan and the chief executive of energy company ExxonMobil for a decade before joining Trump's administration, was replaced with Central Intelligence Agency directer Mike Pompeo, who has since made two trips to North Korea to hold discussions with Kim.More news: National Basketball Association draft lottery: Phoenix Suns get first pick