I was on a totally full United flight from Newark to Tel aviv a year or so ago and it was handled very differently. There was woman seated next to an Hasidic Jewish man who made a fuss about not wanting to sit next to a woman. The crew after 10 minutes of arguing with the passenger offered him the choice of taking his seat or getting off the the plane. He chose to take his seat. Anything other than the solution offered by UA would have been ridiculous. My house my rules.