This is interesting.
I would put the pressure back on the company and try and get them to state, in writing, what they believe you should have done in those circumstances.
If their proposed action would have put the flight at risk (more risk than the TCAS climb exceeding FL391) take it to court if necessary.
I'm no lawyer but I would have thought you would have a good chance of success.
In the meantime it might be nice to know what FL Airbus have actually flight tested the 320 to.