P.Z. Myers talks about "Miller fatigue" and how his approach constititues "putting a coat of Christian paint on the scientific enterprise", but I honestly can't remember where I read him taking genuine heat, as you say, so I suppose I pulled that one out of my a---... Sorry, you know where. Maybe my memory confused him for Ruse, since I'd been reading some of the back and ofrth he;'d been having with Dennett, et al.
As for the fact that scientists, like anyone else, can be open minded, I understand that. But that's not what I meant... Given that it is outside the the "competent reach of science" why would someone buy into, say panspermia? That someone is open-minded doesn't explain why someone accepts any particular idea. I'm just curious as to why the people you talked about found the propositions you were talking about warranted.
All right, lets say Panspermia. There are a number of pretty ordinary arguments that weigh in in favor of it.
In the long haul, the principle that there's nothing special about us has turned out to be correct on quite a few major issues. We aren't the center of the universe, we aren't a special kind of animal, we're part of just one galaxy in millions. We probably don't occupy the unique cradle of life, either.
Also, there is sort of a meta-problem with the long view story of evolution. It's that it seems to be extra-ordinarily fast in the beginning, compared to speed at which it seems to go later. It takes, like 2 billion years to get to Eukariotes from Prokariotes, and then about another billion years to get to multi-cellulars. It's as if the instant the earth cooled, life pooped right out. This does not speak very strongly to the idea that an enormous amount of inorganic experimentation produced life in our ocean. It speaks more strongly to the notion that life is floating around everywhere, waiting for the instant it can take root in some nice newly formed planet.
There is a boatload of other biological oddities that Fred Hoyle goes into in his book on the subject. They're amusing, but I don't take them too seriously, based on the theory that you should bet on the least sensational explanation for something you don't understand much about.
Some examples that stick in my mind: Many tons of spoors, hard-shell viruses, and cysts float out of our atmosphere into space every year. We have no spectacular reason to think that some of these things can't survive viably in space for millions of years. Insects are attracted to a light in insect zappers that has, as far as we know, no natural correspondence on Earth. However, it is characteristic of the light from a certain narrow spectrum of blue-green stars.