One thing that I haven't seen addressed yet is that by charging entry fees (which I personally feel are horrendous BS), the gallery and submitting artist are entering into a business arrangement for the juror(s) to equitably evaluate the entries in exchange for money. To me, that's the problem here: not that your work wasn't selected, or that there were no landscapes (there is no obligation to represent every or any genre of photography in my opinion, even one as big and classic as landscape), but that your work wasn't given the fair evaluation that you paid for.
(FWIW, I really like what you submitted, too; particularly the last two.)
Just take the high road, don't write any letters, but keep entering shows.
Sorry, eddym, but that sounds a little like "shut up and continue to bend over and take it". IMO it's the gallery that took the low road, and calling them out on it isn't stooping to their level. It's making them aware of a situation so they have an opportunity to fix it in the future.
And telling us who the juror is would be a public service, because I know I certainly don't want to pay to have my work "considered" by them. And by charging entry fees and turning submissions into a business rather than artistic arrangement, both the jurors and galleries have made this sort of frank discussion no different than discussing the service you got at Freestyle, B&H, Calumet, etc., and I don't think anyone feels bad about doing that.
Calling people out on bad behavior isn't rude, it's the bad behavior that's rude in the first place.
I'm sure you've heard a lot of whiny complaints from artists in your time as director, but this sounds completely legitimate to me.