Here's the thing. I don't think it's that important.
E.g. Rupert Sheldrake in recent years has openly spoken about his Christian faith. Does this invalidate his work or his integrity as a scientist? I don't think it's even relevant. It's the research that has to be solid and withstand replication and peer analysis.
I can't see how scrutinizing every researcher's belief and conviction would help us gauging the merits of their work.
What I suspect some folks are trying to argue here is that researchers may not be religious in a literal sense (e.g. faithful Christians or Muslims) but rather in a non denominational fashion: e.g. belive in an afterlife, immortality of the soul, God as primal mover rather than the temperamental bearded guy in the sky, etc.
From there goes the allegation that these beliefs are "coloring" their research and the conclusions they make. I.e. those are not objective conclusions, rather they are influenced by previous belief.
Well, surprise surprise, welcome to the world. Scientists are human beings, if this obviousness had to be restated. Find me one without any form of belief or convictions!
If we're not to believe the conclusions of scientists that have a more or less developed spiritual side, I don't see a good reason to believe those who deny any form of spirituality.
Are we going to disocunt Einstein's work because he believed in a superior mind? [
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I find this whole argument a big slice of baloney :D (or mortadella, as it's called over here, the actual salame I mean).
Cheers