It's actually kind of genius.

It implicitly reframes a debate about immigration, to a debate about ecology/sustainability.

Like I'm not defending it or saying it's honest. But as a marketing jiujitsu move, it's actually impressively creative.

That avoids accusations of bigotry which Europe has convinced itself doesn't exist within its domains.

Need to hold them liable to one child per household policy if, for some reason, Swiss start having a little bit more sex and bit more children.

I believe people migrating to Switzerland are largely educated Europeans, so population density must be their biggest concern about migration

To be fair that's not specific to SVP's populist initiatives, the parliament pushes bills with nonsensical names all the time.

It is a population cap, you can read this proposal its like 5 lines of text.