The fact that he was democratically elected is quite moot at this point, given Maduro's apparent commitment to dismantling democracy and moving to one-party rule. His chances of re-election next year are slim to none in a fair election, which is of course why he is now re-writing the rules of the government. He has been trying to strip the National Assembly of power since his party lost control of it (democratically, as it happens, the opposition won nearly two thirds of the seats).

I'm curious what you mean by "a peaceful, negotiated settlement." A solution that does not provide fair democracy and rule of law must be condemned by the international community, and sanctions against the corrupt leadership are precedented and reasonable. Given that most of the people of Venezuela rightly blame the Socialist party for the current economic catastrophe, that would also mean Maduro yielding power. That is how democracy works.