Thing is, the idea that any given issue should only be voted on once has never been how direct democracy works in practice.
We held dozens of referendums on "limiting mass immigration" until one eventually passed. Should the right-wing nationalists have just shut up when they lost the first one in the 1970s? or when they lost the Schengen vote in 2005? or the free movement vote in 2009?
And it was still absolutely scandalous that the immigration referendum wasn't followed. We (EU) would have finally followed Martin Sonneborn's advice and built a wall around Switzerland, to end their special arrangement and free riding off of our security while spitting on our values once and for all. If only our political class didn't have Swiss bank accounts.