I sympathize completely, Tim.
But they are not required to post signs. They can tell you in any way they choose. Of course, we agree completely that their request is not based on any logic whatsoever; quite the contrary.
When you MUST go on private property that requests "no firearms" you would break no laws by concealing it so that their feelings aren't hurt. Of course, this applies after you get your CCW permit!
I can't remember the last time I was there. But I can tell you I was armed. Of course, they couldn't tell, though.