New York is an ‘at-will’ employment state (so is every other state in the U.S., with some limited exceptions). Without a contract restricting termination, generally an employer has the right to discharge an employee at any time for any, or no, reason, providing it is not an act of illegal retaliation or discrimination. There are exceptions to ‘at-will’ employment in New York State, such as termination based on race, creed, color, national origin, sexual orientation, gender identity or expression, military status, sex, disability, predisposing genetic characteristics, familial status, marital status, or status as a victim of domestic violence.
Freedom of speech does not mean freedom from getting fired because of your expression of your opinion (unless an exception above applies).
Please consider that online people are not going to pay your bills when you get fired, and conduct yourselves accordingly.