You bolded the part about "in a certain respect". I'm saying that respect is so limited as to be worthless for any intelligent, meaningful purpose.
Good for you. I don't see it that way. Both are supernatural entities that can be claimed to exist, and in that respect: they are the same.
And imagine the lens had never been invented; no emperical knowledge of germs and more distant celestial bodies. Therefore they couldn't be shown to exist. The conclusion?
The conclusion would be the same. If it can't be shown to exist, there's no valid reason to assume they exist. And that is, off course, also assuming that there are no other, perhaps more indirect, reasons to point in the direction of their existence.
A good example here would be black holes. Einstein's theories suggested they exist. Einstein actually thought he had to be wrong somewhere, becaue the idea of a black hole didn't sound very appealing to him and there was no observational evidence of such bodies. Nevertheless, his theories seemed to be very accurate, which was quite strong evidence that those black holes just might be real. And several years later, lo and behold, they were discovered -
by prediction of Einstein's theories.
So I feel the need to nuance your example a bit.
Having said that, we have nothing even remotely close to such
suggested existence for either gods or spaghetti monsters.
They may exist or they may not. So the FSM hasn't demonstrated anything for which a useful analogy might be helpful.
Now, you're simply misrepresenting the point of the analogy.
The FSM is not (repeat: NOT) a plea for god's
non-existence. In fact, I explicitly stated that "they are claimed to exist, but can't be shown to exist".
To not accept the claim "they exist" as a truth statement
is not the same as accepting the
opposite of the statement.
If you flip a coin, don't show me the results and then assert "it's heads" and I reply "I don't accept your claim as a truth-statement",
it does not mean that I accept the claim "it's tails" as a truth statement.
There's a huge difference.