theres only one occasion i can remember senna actualy doing that and that was against Prost when he took him off on the first corner. But he only did that because he qualified pole but they stuck him on the dirty side of the grid so he said im either coming out the first corner in first place or neither of us are going to get through!
There is a time and a place. MS clearly broke the rules and got punished - rightly so. If you are entering or exiting a corner that is different (which is what i think the senna comment was regarding) you have the right to commit to one move and then you have to stick to your line. If the one move is a risky move then so be it, but you dont do it on a straight at 200mph and you dont make more then one move (which in my opinion MS did)