Is it ethical to force graduate applicants to decide before they hear back from all schools?

The April 15 Resolution technically applies only to offers of financial support, not to offers of admission. There’s no clear-cut rule saying a school can’t require an early answer for admissions, saying it’s unethical to do so is a difficult claim to make. To my mind, it’s definitely poor form and suggests that the program is either (a) quite prestigious and doesn’t need to worry too much about yield or (b) rather noncompetitive and desperate for enrollees, but they’re risking rejections as well with the hardline approach they’re taking. (Funny how extreme cases in different directions can take the same approach!)

However, given that the program in question is unfunded, it's completely unreasonable for them to expect you to commit irrevocably to an offer of admission, particularly since they are effectively not committing any additional resources to offer you admission. I would thus feel no moral qualms whatsoever in withdrawing my acceptance if another, funded program were to make an offer before the April 15 deadline.

Ethical for them to have this deadline. Also ethical for you to cancel the acceptance of an unsupported position if you later get an offer for a supported position elsewhere. Doing this would burn bridges only between you and the admissions folks (not professors) but keep in mind they have backup students waitlisted to account for cancellations.

I have another perspective on this. They are well aware of what they are asking for and the implications for the students. In fact it seems obvious that they are deliberatly forcing an early decision for that very reason. My question then becomes, if they are acting this way now how will they act after the students have enrolled? Is that really a school that seems like they are putting the quality of the education first or are they more likely to squeeze as much money from you as possible? If you have to ask if your prospective school behaves ethically at the first contact I would be very sceptical to their entire business. Granted, I'm from a country where all education are free so YMMV.