That decision is absolutely not the place of the developer. Failing to support a particularly market segment has implications far broader than simply the bottom line dollar value of each user. Even if those users bring in zero revenue it can still be worthwhile developing the code base so that they're supported. This sort of thing is an example of something that you, as a developer, simply aren't equipped with the necessary information or knowledge to make decisions about on your own - it has to be a collective decision informed by developers, marketers, product managers, and C-level managers.
A trivial example - the decision whether or not to go with a single page Javascript application design versus rendering pages on the server can be influenced by user demographics but have a massive impact on everything in the business from hardware costs to how you integrate payment reporting in to the workflow of the business.
Any developer who puts their needs in supporting particular users over the requirements of the company as a whole, frankly, probably ought to be shown the door. They don't understand how the whole business process works and they will almost certainly screw up something really important later.