Lots of people get laughed at though - fat people, bald men, men in cycling gear, homeless people, etc, etc - and none of these are 'protected characteristics'.
'Gender reassignment' is a ridiculously vague category to be included. People have the choice to dress in such a way that doesn't make them stand out and face ridicule - women, disabled/disfigured people, old people and people from ethnic minorities don't have any choice about their condition.