Yeah, what ever you do not mention the ultimatum as being reasonable. Taking the stance that they were warned, given options and didn't take any of the options, and so suffered the consequences is rather badly received. The Reaction I got surprised me when I made a comment about it where a Frenchman could see it! It was a bit like being suddenly savaged by a puppy poodle out of nowhere.Once over I worked with a French Algerian, born long after 1940 but who was very bitter about Operation Catapult. 60 odd years (when I knew him) after the event it was still a pretty contentious issue that was taken very personally.
The view I got off a Frenchman was they were only following orders (getting some practice in are we?), and that an armistice was signed, so it was all above board etc etc. Pointing out that by staying meant they were now a German Fleet and thus Target is apparently naughty as well.
There's a bit of a mental car crash however, if you then point out the Free French Forces who bailed to the UK.