There's more historical context here. Anti-vax is a Republican talking point now, but the original anti-vaxers were granola moms on the left and anti-government sovcits on the right. Canada has plenty of both.
I feel like the 1980s in North American liberalism is a bit like...actually just like the 1980s with regards to race and civil rights in America as well: a bunch of
really important stuff happened, but we're all supposed to pretend that it didn't.
In this case it wasn't the Southern Strategy, but its opposite counterpart: The Democratic Leadership Committee. The official myth is that by 2000, the Democratic Party was simply a centrist technocratic coalition, and because the guy taking credit for it was also a sex pest who we wanted to forget after Jan 20th 2001, there was no reason for anyone to consider how the Democratic Party kicked out the New Agers and LaRouches and assorted other left-wing versions of the John Birch Society.
It just sorta happened, and right in time for some guy to become President just for the blowjobs. But fortunately today's Democratic leadership would never impose any sort of litmus test like that. It's a really slippery slope from there to rejecting candidates who only have a single Nazi tattoo from 20 years ago...