On what planet do they owe you any specific intent?!?
You don't need to let the atheists "off the hook," because they were never ON it in the first place.
There's no obligation -- legal or moral or ethical -- for anyone to make some kind of "matching" message to "promote the season," GOT IT?
All of your nonsense about presuming intent, assuming intent, or even coming up with a perfectly reasonable and substantive analysis of intent is COMPLETELY IRRELEVANT, because they don't owe you any kind of obedience or compliance.
Got it? YOU ARE NOT OWED ANYTHING BY THEM.
Also, to be absolutely clear:
No longer enjoying the unearned PRIVILEGE of unchecked social dominance in a public space...is NOT a case of being victimized.
Much as with white nationalist narratives of U.S. history no longer enjoying unchallenged over-representation in classrooms, the mere presence of countering information and other views is not an infringement. So too with the (no-longer-unchecked) privilege of those pushing a religious display in a public park.