I rather agree with this, but would go further and argue that you can hold that both Petain and de Gaulle were right. That is, if one imagines onself as a Frenchman in the summer of 1940, one might think easily that Petain was right to save what could be saved - albeit at great cost and damage - to preserve something of the idea of France and avoid the humiliation of seeing the entire country occupied by German forces while also hoping that de Gaulle and his followers would eventually prevail. Vichy, in this view, would be nothing more than a holding operation - albeit one that was often craven and squalid - before the eventual Allied victory.“
Can one hold that both Marsall Petain and General de Gaulle were French patriots? I think the answer to this one has to be “yes.” You can’t hold that both were right, but you can believe that both were acting sincerely out of patriotic motives – that both were doing what they felt was best for France as France.
Granted, such a victory seemed impossible in 1940 and for many it must have seemed that having lost 100,000 men in the Battle of France there was little point in wasting more French blood in a hopeless cause. Vichy was a matter of expediency in a desperate situation. That there were willing collaborators doesn't mean that every Frenchman who served Vichy was doing so enthusiastically.
Nevertheless, Petain's patriotism also relied upon de Gaulle for it was the existence of the Free French in exile that afforded the possibility that the nightmare of occupation might, however unlikely it seemed, be temporary. It's easy, in hindsight, to say that collaboration was shameful and of course it often was. But it was also, alas, realistic and perhaps inevitable.
So, in other words, I think one can argue that in the circumstances of 1940 both Petain and de Gaulle were patriots but that their patriotism was operating on different timetables. That is, Petain's was a patriotism for 1940, saving what could be saved, whereas de Gaulle's was a patriotism that took a longer view, hlding out for an improbable victory some time in the future after which France and the Idea of France could be revived.
This is actually somewhat akin to the Chamberlain vs Churchill debate. Were they both patriots at Munich? I think so and, likewise, I think one can argue that Chamberlain and Churchill were both right about Munich, just in different ways and, again, with on different timetables.
PS: For obvious reasons, I consider this book one of the better novels about France in the Second World War.