It's an astonishing tweet. Firstly, the march was anything but democratic. It's sole purpose was to instigate the reversal of a democratic vote - the Leave vote of June 2016. Secondly, his reference to a "fascist state" was something that you'd expect to find on the pages of some obscure Marxist publication, not attributed to a Member of Parliament. In any case, surely the only people that could be described as 'fascists' were those marching to overturn a democratic decision!