Useful for anyone needing to speak up to a GA or FA in similar circumstances? The CoC.

21 REFUSAL TO TRANSPORT
UA shall have the right to refuse to transport or shall have the right to remove from the aircraft at any point, any Passenger
for the following reasons:
H) Safety – Whenever refusal or removal of a Passenger may be necessary for the safety of such Passenger or other
Passengers or members of the crew including, but not limited to:
16) Passengers who have or cause a malodorous condition (other than individuals qualifying as disabled);
17) [unescorted] Persons who are mentally deranged or mentally incapacitated whose behavior may be hazardous to
himself/herself, the crew, or other passengers.