By and large, I find an alternative. My physician, who is a collector & shooter, was careful to ensure that the "co-op" of which he is a part put up a non-compliant (per state law) sign, mollifying the hoplophobes and giving him, me and others legal cover. I changed copy shops when the sign went up.
Heck, I had just bought two new cars from a Honda dealer within a year; when the sign went up and the sales manager got snotty* about it, I took my business to a more enlightened Honda dealer to purchase a new Pilot. Needless to say, the posted dealer will never sell a car to me or get a dime of my PM or service work.
On the other hand, my wife's haircutter's buiding owner posted the building. I'm not going to ask her to terminate a long-standing relationship. After all, he has no influence over the posting. So the answer is, "It depends." But the decision to continue to patronize a posted business is a rare exception.
Regards,
Walt
*"Why are you posted?"
"We have a lot of money here."
"More money than XXXX, my personal bank, or YYYY, my commercial bank? I don't think so. and they are not posted. Neither is my supermarket, or any of the three drugstores I patronize, nor any number of other establishments where I trade."
"Well, said you wouldn't spend your money where the sign made you feel unwelcome; why are you here?"
—and gone was I, yes.