First off, the "guy" cannot have you charged with anything unless the "guy" is a prosecutor (in which case, perceived threatening communications from you could be very serious). He can go to a judge and request a protective order and he can go to the police and report what he believes to be a crime. But, for either, the burden is on him to convince the judge/police/prosecutor that you committed an actual crime or that you pose a reasonable threat.
However, souperdave is correct. Without knowing the actual contents of your facebook post, along with any other circumstances that would add context, it is impossible to give any opinion of whether a reasonable person would conclude that the post rises to the level of:
2903.211 Menacing by stalking.
(A)(1) No person by engaging in a pattern of conduct shall knowingly cause another person to believe that the offender will cause physical harm to the other person or cause mental distress to the other person.