I think “petty things don’t matter” connotes that the differences are small on an absolute scale and that working together demonstrates this, not that the differences are merely small in relation to the goal on which everyone works together. The latter is honoring Nazis for their sacrifices; the former is saying “the fact that Nazis can sacrifice shows that it’s not important to oppose Naziism”.
I think “petty things don’t matter” connotes that the differences are small on an absolute scale and that working together demonstrates this, not that the differences are merely small in relation to the goal on which everyone works together. The latter is honoring Nazis for their sacrifices; the former is saying “the fact that Nazis can sacrifice shows that it’s not important to oppose Naziism”.