And at this point we are discussing semantics
Of course we are.
However, I do believe there's a fundamental difference between this and other examples you've given such as the oak tree. Bitcoin, being a currency - and a purely digital one at that - is defined by what people think it is. If the system continues to work as it does now, but people stop believing in it, it becomes meaningless.
Whereas the oak tree is still there regardless of whether we look at it, talk about it, call it different names. With the oak tree, the specific configuration of atoms matters. With Bitcoin, the agreement of people matters.
Hence, we have the power to mutate Bitcoin with the power of thought and agreement, in a way we cannot with the oak tree.
Notably, this has happened before (P2SH and some bug fixes come to mind). People agreed that Bitcoin should be changed, and viola, Bitcoin was changed, without anyone supposing we're now using an alt.
This discussion has practical consequences beyond the OP's opinion. When I accept bitcoins as payment, I do so because I believe they will have value now and in the future (as with any other currency). I believe this because I believe Bitcoin will be used, and that there will be no more than 21M bitcoins. "Used" is a human-centric concept and thus is influenced by perception and marketing. If people use the name "Bitcoin" to refer to a new protocol, it has a different effect on the survivability of the old protocol than if people used a different name.
So "will a protocol that has a different inflation schedule than the current Bitcoin exist" is a different question from "will a protocol that has a different inflation schedule than the current Bitcoin exist and be called 'Bitcoin'". A positive answer to the latter doesn't bode well to the value of bitcoins I can currently obtain, thus a negative answer to it is what I need to be assured in accepting bitcoins. This again is a practical consideration, not a purely philosophical one.
