Sakura - you are making some sweeping statements there! I am not sure that the Army regiments/Royal Marines/RAF Regiment currently fighting in Afghanistan would recognise your description of the lack of physicality that war involves.
There are two main aspects to barring women in combat roles. One is physical. In jobs where you may be required to cover a lot of ground in the searing heat/freezing cold, carrying HUGE amounts of kit, and then close and fight with the enemy, you need to be very fit and strong. It is indisputable that women, even after as much (and more) physical training as men, are rarely as physically strong. This is because we do not build muscle in the same way. Studies show that women have much higher injury rates in even attempting to reach the same fitness standards as men in these situations. There are of course exceptions - women who are awesomely fit and can maintain the same standards as men, but they are quite rare.
The second aspect is the issue of how men in combat behave when they have women fighting with them. There is some (limited) evidence here, mainly from the Israeli forces, that shows that it has a clear detrimental effect on decision making and behaviour. Now there is an argument to say that men should just 'get over' this arcane behaviour, however how many deaths will occur whilst people gradually adapt?
To be honest, I would like women to have full equality of opportunity in the Armed Forces - I served for 7 years and didn't feel discriminated against. There are women already serving in roles which put them almost in that role already (female pilots/Int officers at the front/EOD officers/medics.) They are all under fire, and most of them will probably be involved in the return of fire. Perhaps it will potentially come to pass - who knows....but it isn't a black and white issue.