After a few days of pondering I came to the conclusion (which is only my opinion) that the division of the simple and progressive forms in Modern English is akin to the use-mention distinction in analytic philosophy.
The simple is used to assert something, while the progressive is used to point to this assertion.
Here's an example to partially support my hypothesis:
(I say) I refuse to go.
(The listener says) Oh, so you're refusing to go?
Here is yet another example:
(Someone says) I think guns kill people, not people.
(I say) Are you saying that we should ban bearing guns?
None of the two examples above have the "happening at the moment" reading.
Am I on the right track here? If I am, where can I read more about this?