While that's probably true the optics are pretty obviously terrible.
If Walmart engaged in a price war with a small mom and pop bakery across the street I would be similarly unimpressed (disgusted, really).
A small bakery cannot engage in price manipulation for a meaningful time or volume to oust competition, that activity is completely different category.
Anyways the fundamental problem with most bookstores that aren't Barnes and Noble is that they all do a terrible job of having the things I want to read. When the local artisan bookstore won't bother to stock RA Salvatore or even fucking Tolkien because it's too "low brow" I don't have a whole lot of empathy for them. I actually do enjoy bookstores when they aren't merely a far more inconvenient way to order books from a large corporate distribution center.
Which is to say, almost nobody cares.
There is no anti-trust law saying you can't have a sale the same day your competitors are having a party.
Generally, when anti-trust cases go to court, they will use individual cases like these of anti-conpetitive behavior as evidence to build a case of a pattern of that type of behavior.