> Opening your wallet sends a signal to the receiving business to keep doing what they're doing, even if we all know it's bad.

That is exactly my point, though. The signal from my personal transactions isn't going to be enough to change anything. It will be drowned out by everyone else.

Of course, you are right that if enough people closed their wallet, then the business would have to change. However, that is STILL true even if I keep my wallet open. If N people stopping their shopping at a store would cause it to close/change its practices, then surely N-1 people stopping their shopping would also cause it to change. I could still keep shopping their, get the benefits while they last, and then switch once it finally goes out of business.

Of course, you might reasonably say, "Well, if everyone thought like you, then the change would never happen!" True, but my decision does not change anyone else's decision. The other people won't even know my choice, it isn't going to make other people boycott.

You could argue that people will listen to what I say, and I could influence them. That is true, but that is again independent of whether I actually 'vote with my wallet' or not. The influence I have on other people is the same whether I tell them not to shop there and I also don't shop there, or if I tell them not to shop there but secretly shop there myself.

Obviously there is some other morality at play here, but it isn't as simple as invoking the direct signal I am sending by choosing to shop somewhere or not.