Thank you. A false dichotomy seems to be another possibility. It's not a phrase I've seen much, so I have some reading to do.

The characteristic thing about the type of argument I have described above is the implicit, almost "sneaky", assumption that theory B is right. It's introduced completely casually, as if its validity is intuitively obvious. Yet, as a scientific theory, theory B is just as subject to doubt (in my opinion) as any other theory, and its popularity is no proof of its validity. If one happens to hold to the popular model, one should still be able to articulate the fundamental evidence for it, whether that be an ab initio proof or some experimental observations, or both. There's something knavish and underhanded about this type of argument that really gets under my skin, even when I'm not one of the disputants. I thought there might be some famous name attached to it, like a politician's name, or the name of someone in a famous novel or play, who used this type of argument to "win" his case, even though some people could see it was more of a trick than a good argument.

Oops, I forgot to preview my last response before sending it, and I got some formatting in there that messed it up. Sorry about that. Please ignore the italics at the end of that last post. "Johnsonism" was supposed to be an example of the kind of "name" for this type of argument that I was hoping for.

Thank you both for quick responses. "Prejudicial thinking" is right on, but it may be a bit to directly insulting if I use that in an argument with somebody. I was hoping to be able to say something like, "Ah, but your argument is basically a Johnsonism: you're assuming its truth without being able to say why it is true, and then you're just showing that it gives different results from this new model, and then concluding that the new model must be false" . But at least Damer's is a published work that I can cite if I need to, so thank you for that one.