Does a man on disability have to pay child support if divorced?

If the court orders it, he does.  There is not automatic exclusion for someone collecting disabliity.

Florida Child Support Statute 61.30 defines what income is to be included in calculating child support.  Disability benefits is one of the type of benefits that is included in income to determine each parents' child support obligation.  Child support is based on both parents' net income.  If the man is receiving social security disability, his child should receive a benefit from social security as well.  This would offset some of the child support obligation the man would owe.  You have to apply for the social security benefit on behalf of the child.  They do not automatically give it to you just because you are on social security disability.