I think that if you give in the offering then you can tell the preacher what to preach. For that matter, just walk up to the preacher - any preacher - and tell him or her what you think they should preach, whether you give to that church or not. Don't worry if they're in a different denomination or even a whole different religion, just tell them what to preach.
Let's all just show up at some church this Sunday and start telling the people there what to preach and teach. Let's go to a "gay" church and tell them they
can't hire gays, then run over to a Fundamentalist Baptist church and tell them they
have to hire gays. We can do that. Let's find a bank employee to go along with us, and an IRS man and someone from the circus.
It's a free country - say whatever you want. The banks can say whatever they want.