Wow supergenius you've been in a bit of a strop haven't you?
It is perfectly legitimate to change subject areas, especially at Masters rather than PhD level. You may need to do some additional reading at the start to make sure you are on top of things, but most unis will be happy to take you as long as you show real motivation (so you do need to be far clearer on what you actually want).
My undergrad was a mix of language (an obscure one), literature and history, my MA was International Relations, the dissertation for which ended up being in ethical and political philosophy (and yes I got a distinction for it). My PhD is now political philosophy with sociology and human geography, and I am doing very well at it. So if people are patronising enough to say you can't successfully move disciplines, then they are being rather narrow-minded (rather sad from a postgraduate)