I think the point here is "Is the past fixed, or can it be changed?"Read back, many people have given reason one could be invented.
Dave was responding to the FEP statement, not the time machine issue. The one in which it was said time travel isn't possible because of FEP.
Many reasons have been given as to the why it may be possible in the future and also why not. But they are all just hypothesis and speculation. I don't know what more you want.
If the past is fixed and you went back in time, you wouldn't be aware of it, as you would be 'reliving' the past exactly as it was.
If it was possible to 'change the past', this would require such a huge amount of instantaneous energy (to re-arrange everything in 'no time at all') that this would contravene everything we know about physics. Unless, of course, we use antimatter (which, apparently, travels backwards in time) to create this energy when it, and the matter it meets, is anhialated.
This then begs the question 'Would we want to be there when all the matter around us is anhialated?'.
Unless, of course, you can come up with an alternative mechanism?