After many weeks of a stressful situation with extensive hours and demands, employee cracked and responded in a way they shouldn't (spoke harshly to boss in front of others in the office) in response to something relatively innocuous.
Result, a disciplinary hearing for unprofessional behaviour - explained reasons /mitigation in the meeting but these were essentially dismissed ("should have spoken up before" etc) and the reprimand upheld and put on file for a period. Didn't speak up before because of already feeling stressed and intimidated due to various company politics etc. some of which had already been unofficially brought up but disregarded.
Employee now constantly in fear of something else generating an additional/further warning and as a result willing to do any unreasonable hours etc to get things done and not speak up.
Is the warning justified or what should have been done differently?