I’m going to have to side with Apple here (and I think I just threw up a bit in my mouth). iMessage is a service that they provide, and they’re well within their rights to restrict access to paying customers. iPhone users pay for it when they buy their latest shiny object; users of other brand devices don’t.
If you really want iMessage that desperately, buy an iPhone. That’s not worth it to you? That’s fine, but you can’t have it both ways.
At this point at the latest it would be much easier (not to mention more reliable) to get your iPhone-owning friends or family to use another messenger that’s not restricted to one single manufacturer. There are several apps that offer more features and more privacy than iMessage and are officially supported (not relying on unofficial hacks) on every modern smartphone.