If you are confident enough to face it, I don't see any ethical problem with inducing a charge.

Large animals are going to take several minutes to die without a brain or spine shot, so if approaching the animal too closely and upwind and towards its head induces a charge and a quick brain shot death, I don't see that as being any different from shooting it again at 50 metres and it still taking another two or three minutes to die.

Who hasn't sat by quietly for two or three minutes waiting for buffalo or eland shot to the heart to quietly die? I call letting the animal die in peace, also respecting the animal.

As for human emotions, a buffalo is merely defending itself as instinct has instilled in it for thousands of years.