If a majority of experts agree on an issue, a rationalist should be prepared to defer to their judgment. It is reasonable to expect that the experts have superior knowledge and have considered many more arguments than a lay person would be able to. However, if experts are split into camps that reject each other's arguments, then it is rational to take their expert rejections into account. This is the case even among experts that support the same conclusion.
If 2/3's of experts support proposition G , 1/3 because of reason A while rejecting B, and 1/3 because of reason B while rejecting A, and the remaining 1/3 reject both A and B; then the majority Reject A, and the majority Reject B. G should not be treated as a reasonable majority view.
Positions that fundamentally disagree don't combine in dependent aspects on which they agree. On the contrary, If people offer lots of different contradictory reasons for a conclusion (even if each individual has consistent beliefs) it is a sign that they are rationalizing their position.
An exception to this is if experts agree on something for the same proximal reasons. If pharmacists were split into camps that disagreed on what atoms fundamentally were, but agreed on how chemistry and biology worked, then we could add those camps together as authorities on what the effect of a drug would be.
If we're going to add up expert views, we need to add up what experts consider important about a question and agree on, not individual features of their conclusions.
Some differing reasons can be additive: Evolution has support from many fields. We can add the analysis of all these experts together because the paleontologists do not generally dispute the arguments of geneticists.
Different people might justify vegetarianism by citing the suffering of animals, health benefits, environmental impacts, or purely spiritual concerns. As long as there isn't a camp of vegetarians that claim it does not have e.g. redeeming health benefits, we can more or less add all those opinions together.
We shouldn't add up two experts if they would consider each other's arguments irrational. That's ignoring their expertise.