It's a technique akin to consensus cracking. They pick a few conspiracies that they make up or some scarecrow versions of conspiracies, then debunk those. With sufficient debunkings out there, "the science is settled" and they can use that as a club to beat any other kind of dissent.

Short of a blood transfusion, I don't think a jabbed person is going to cause you any direct harm being around them. Indirectly on the other hand... Who knows when their ticking time bomb goes off.