[silverspoonin]

>There is no requirement to evaluate the truth value of an ill defined, nonsensical or self-contradictory claim.

Calling a claim "ill defined, nonsensical or self-contradictory" is already an evaluation of it's probable truth value.

> Note that the position that OP advanced, and which you appear to be defending is that the bare fact of the existence of a consensus should be treated as primary evidence on its own.

Actually, the person you responded to clearly stated: "how should I evaluate truth in a subject matter that I myself don't have a doctorate in". For someone well-versed in the area, or at least with enough free time to become sufficiently acquainted with it, going to directly to primary evidence is the optimal approach. However, in the situation described by OP, were they are limited in the amount of time and cognitive capacity they can invest, then basing decisions on such "Secondary evidence" as expert consensus is the rational approach.