Your school has a duty of care towards its employees and governors
This means that staff members, including the headteacher and governors, should not be placed in dangerous or upsetting situations. You shouldn't be expected to attend meetings where parents or carers are behaving aggressively, or to respond to abusive communications.
To support this, your school should have clear policies in place, such as a parent/carer code of conduct or a policy on dealing with abusive visitors. These should clearly state that meetings will be stopped or cancelled if a parent or carer does not adhere to the expected code of conduct.