I send stuff to be printed on a daily basis, these days as hi-res tiff or more often PDF. I also found in the past a couple of printers who were able to accept a xar. file and weave their magic from that.
I find printers who lay down too many restrictions on what they are 'prepared' to accept are no more worth my while bothering with as I appear to not be worth their while at least trying to please me as a potential customer.
I agree, let them find a new customer or at least you find a new printer. There are plenty out there who will do the job and make a good job of it.
The printers who don't want to be bothered with you obviously have enough customers using the 'correct' software anyhow.
Derek