I agree. Anti-vax is not a mainstream view and thus is not going to get the same coverage in the mainstream media.
I don't either although I do think it plays a part. I think some PPs have brought up some other reasons that might explain the backlash.
Really, it goes both ways and I doubt plays any more or less a roll for either side. I saw lots of judgment from anti-vaxers (and I don't just mean non) long before there was much mainstream backlash against non-vaxers.