Difference between FACT and INFERENCE
Let us recognize that the Malysian PM is most likely not trained as a physicist (an inference of mine), and when he starts hinting at what he thinks are facts, he is actually speaking of deductions, or inferences.
We already have the Facts of the take-off, destination, last radio contact, message, and no transponder signal. We have as Fact the last known Heading and Altitude.
We have these indications of "pings" being picked up, with no further details. That event gets transposed in the "fact" that the ping(s) came from this aircraft, but that is not fact, that is inference. From that, we have the deductive inference that this aircraft is still flying around at altitude for some 7.5 hours after last contact. Again, this inference gets transposed into "fact." Except it isn't.
Absence of events are also facts. Factually, nobody has seen this aircraft. Nobody has reliably reported seeing it land in Tajikistan, or anywhere else. Nobody has seen it crash, and nobody has seen any wreckage. There is no factual basis to indicate that it has crashed over water. There is no factual basis to say it has not, conversely. Equally, there is no factual basis that it crashed into terrain; nor that it did not.
There have been some rather short, and snippy, even pejorative sniping by highly experienced professional pilots at other pilots, which leads me to the inference (not fact) that everybody's nerves are getting frayed. And you fellows, who are historically exceptionally cool under pressures that would crack any mere mortal, should know better. Since you have ice water in your veins, now is the time to show it.
We can make some inferences based on plausibility. Is it plausible that this aircraft is still flying around, thousands of miles from where it should be, at altitude, and not near any place to land, some 7.5 hours after last radio contact? Nope. It is plausible that the aircraft flew right across India for hours and was undetected? Nope. It it plausible that it flew undetected towards Perth? Nope. Is it plausible that it was taken over by hijackers, flown around by amateurs, landed in the dark on the undercarriage on some 7,500-ft surface capable of handling the weight, without lights or any ILS - and nobody in authority knows anything about it? Nope. Is it plausible that it splashed and left no vast field of debris and bodies - as all other water crashes have done? Nope.
Is it plausible that, after 7 days with no facts linked directly and observably to this aircraft, and that we still do not know what ocean (or land mass) this aircraft is in, we may never know? Unfortunately, Yes. That is plausible.