I wouldn't have thought a zombie march funny. Fun, perhaps but not funny.

It never occurred to me either that a Memorial Day zombie march might be offensive. After all, zombies aren't dead, just undead, and Memorial Day remembers people who have given their lives in service to their country. It isn't a remember the dead day, per se. Whereas Easter commemorates someone who died and rose from the dead, and I would find the suggestion that he is zombie-like offensive.

Of course, you know my bias.