hah in lee vs gaara guy sensei pushed his sand away with his single hand.. plus if a huge mass of water can be pierce than why not sand??
everything is logical in manga depending on plot btw.....
Plot does not make things happen
because of logic, it makes them happen
in spite of it. Guy scattering Gaara's sand was a deliberate and forceful action, and was essentially equivalent to the sand dispersing as lee was punching and kicking it, the sand isn't just going to scatter away because he's discharging sweat/energy opening the gates, aside from that,that discharge only occurs when the gates are initially opened, during which time the user is just standing still super saiyan style anyway, so that interval isn't being used tactically. Sand that is being actively shaped and controlled by chakra is nothing like standing water, that isn't comparable for obvious reasons.