They have the "right" to have a revolution too - many countries treasure the revolutions they had. They can amend the constitution and make another democracy. They can also amend the constitution and make a dictatorship. Or just have a dictatorship without bothering. Those do not need constitutions at all.

To have a vote that turns a democracy into a non-democracy is a meta-democratic vote, not a democratic vote. Abusing a democratic system to surreptitiously make a non-democratic system is just a caveat that dictators find convenient to use.