"If you call the turn you have to call river" theory Q

[Keyser.]

Instead of derailing a few other threads with this discussion I want to have it here.

I see this line used all the time in strat threads (or the variation "If you fold the river you should just fold the turn"), but I question if it's a theoretically sound piece of advice.

Why can't I call the turn and then get more information on the river and change my mind? Why does a decision on one street mandate that I make the same decision on a future street?

example hand

150bb stacks, 6 handed
MP raises to 4bbs, folded to you in the BB and you call with A[img]/images/graemlins/heart.gif[/img]T[img]/images/graemlins/heart.gif[/img]

Flop T[img]/images/graemlins/spade.gif[/img] 6[img]/images/graemlins/club.gif[/img] 2[img]/images/graemlins/diamond.gif[/img] (pot 8bbs)
You check, Villain bets 7bbs, you call

[/b]Turn:[/b] T[img]/images/graemlins/spade.gif[/img] 6[img]/images/graemlins/club.gif[/img] 2[img]/images/graemlins/diamond.gif[/img] [5[img]/images/graemlins/club.gif[/img]] (pot 22 bbs)
You check, Villain bets 19 bbs, you call

River: T[img]/images/graemlins/spade.gif[/img] 6[img]/images/graemlins/club.gif[/img] 2[img]/images/graemlins/diamond.gif[/img] 5[img]/images/graemlins/club.gif[/img] [2[img]/images/graemlins/spade.gif[/img]] (pot 41 bbs)
You check, Villain bets a lot, you fold.

The river deuce doesn't change anything really, but I think we're ahead on the turn often but very rarely ahead on the river. In a situation like this can you profitably call the turn and still fold river depending on the card/his action? thoughts?