For future reference, it's important to keep in mind that while a human can kill a Servant, a human can't fight a Servant. Only freaks like the perfect half-oni or the Nasuverse's poster child for efficiency can do that. 

With that in mind, in a situation like this, while a Master being able to respond to something like a normal golem would be perfectly feasible, trying to dodge the attack of a Servant-level golem is analogous to trying to dodge a Saber swinging their sword. In this particular case though, it's not a sword but a castle tower, which makes this quite a few times more problematic than even dealing with a Servant's attack. 

This applies to all Masters in this war. Unless the Servant is playing around or very serious planning/precautions have been taken prior to the fight, it should be assumed that attempting to react to a Servant's attack will be pretty useless. But then again, that's why you have your own Servant. 

Well, unless you're Nakae.