They should challenge him to get a peer review through a respected journal instead…

Never argue with an idiot. They’ll drag you down to their level and then beat you with experience.

Anti-vaxxers are already too stupid or too mentally ill to be swayed by things like facts or evidence. Engaging them would not only be a waste of time, it would paint a target on this scientist’s back for ever kook and nutter whose delusion is threatened by them. And the last thing that any expert should do is give these nutbags any legitimacy by engaging with them.

No scientist should tarnish their own credibility by giving these grifters a platform for debate.