Is your union rep doing their job?
How to handle management during a meeting
If your company has a union, the question is always, "what are my rights as a union member" when things go sour at work. All unions have a grievance process but not all grievances are a winnable situation. Pick your battle carefully.
Your rights as a union paying member is to know first and foremost, you do not have to speak with management in the workplace without a union representative present. Management will not willfully offer the representative either. You must request someone at the time of meeting. Management may also say this is not an investigatory meeting. Keep in mind though, any questions management asks you could jeopardize your employment future. If management still refuses you representation, you can remind them you are an union paying member.
If management finally brings in your representative to the meeting, it is the representative job to take complete notes! Now re-read this sentence... complete notes (keyword)... the notes should have who is all present at the meeting and everything that is said. Your representative has the right to pull you out of the meeting at anytime, (time out, to advise, or even to calm the situation at hand). A representative also has the right to interject in the conversation if they violate your rights in anyway. (shouting, verbal abuse, threatening)
After the meeting, it is your right to speak with your representative. Management cannot refuse this option.