If a business wanted to charge me to change a baby's diaper in the bathroom, I'd just do it right on the table or whatever in the middle of everyone. Let's see how your business does when everyone is seeing and smelling that business. I hope it's a restaurant.
I expect that customers will not blame the business for that. They'll just think you're an inconsiderate person, like all the other parents who think a table where people eat is an appropriate place for their child's faeces...
Making the other customers suffer, and potentially get ill, isn't a reasonable response to a business doing something shitty. Just don't go to restaurants that don't provide baby-changing facilities. Don't expose innocent people to your baby's shit.
Collateral damage in a just war. Don't patronize restaurants that charge for the restroom and you're in the clear there, while also being on the morally correct side of history.
I don't patronise restaurants that charge for toilet use. But that doesn't put me on the side of parents who put their baby's shitty arse on tables where people eat. Both sides of this "war" are shitty people that I want nothing to do with.
My local authority in East London pays local cafes a small amount if they make their toilets available to the general public and display a sign on the door. This feels like a good pragmatic solution to me.
Do like the Romans did: ask for a recliner so you can get on your side to fart and piss freely while being fed by women whom you throw scraps of food to pick up from the floor... /s