Being "protected" does not mean, however, that an employee is protected from any employment action and enjoys some kind of immunity because of his FMLA or ADA status. For instance, when a lay-off takes place, and employee who is on FMLA or ADA leave is subject to lay-off just like any other employee. It would only be illegal to choose an employee for lay-off because of his FMLA /ADA status.
The same applies to employment terminations. A disabled employee who engages in some kind of misconduct or violates an employer's policy can be lawfully terminated just like any other employee who never applied for FMLA leave or ADA/FEHA leave or other accommodations. Being in a "protected" class is not a shield against all harm. It's only a legal remedy against being treated differently because you are a member of that class.