Do major scientists say "is fine tuned", or do they say "appears fine tuned"? You're using both expressions as if they are the same.
Not arguably scientific at all. It is scientific. Not pure speculation either, that's just silly. Any hypothesis based on math, quantum physics, as the multiverse is, cannot sensibly be called pure speculation or arguably scientific. And endlessly parroting "the universe appears fine tuned" won't make words like "appears" and "fine tuned" turn into "intelligently designed". According to Stephen Hawking, gravity is your so called fine tuner which doesn't even require 'the multiverse'.
They say it appears fine tuned in order to then explain it with their pure speculation of a multiverse.
The multiverse is pure speculation. Just because there are 10 to the 500 possible solutions provided by string theory does not in any way establish they are real universes. Just as a multiverse is a conjecture for Hawking. Hawking never says its real.
The multiverse (or meta-universe) is the hypothetical set of multiple possible universes (including the historical universe we consistently experience) that together comprise everything that exists and can exist: the entirety of space, time, matter, and energy as well as the physical laws and constants that describe them. The term was coined in 1895 by the American philosopher and psychologist William James.[1] The various universes within the multiverse are sometimes called parallel universes. The structure of the multiverse, the nature of each universe within it and the relationship between the various constituent universes, depend on the specific multiverse hypothesis considered. Multiple universes have been hypothesized in cosmology, physics, astronomy, religion, philosophy, transpersonal psychology and fiction, particularly in science fiction and fantasy. In these contexts, parallel universes are also called "alternative universes", "quantum universes", "interpenetrating dimensions", "parallel dimensions", "parallel worlds", "alternative realities", "alternative timelines", and "dimensional planes," among others. http://en.wikipedia.org/wiki/Multiverse
As skeptical as I am, I think the contemplation of the multiverse is an excellent opportunity to reflect on the nature of science and on the ultimate nature of existence: why we are here⦠In looking at this concept, we need an open mind, though not too open. It is a delicate path to tread. Parallel universes may or may not exist; the case is unproved. We are going to have to live with that uncertainty. Nothing is wrong with scientifically based philosophical speculation, which is what multiverse proposals are. But we should name it for what it is. â George Ellis, Scientific American, Does the Multiverse Really Exist?
Conjecture based on math and quantum mechanics cannot sensibly be described as pure speculation. Conjecture based on nought but wishful thinking, intelligent design and creationism for instance, is reasonably described as pure speculation. Or more accurately, blind unfounded guessing.