@leon, first i take it you are cis (and male identified) Second, how would you feel if people constantly refered to you by a female name, and pronouns, expected you to fill female stereotypes and dress in whatever your cultural norms for feminie are?
Also, it is not 'an idea' which you thinks is stupid. It is the experience of other which you are dismissing because you don't understand or appreciate it.
This is comparable to saying 'rascism' is stupid, i don't experience discrimination based on the colour of my skin, and i don't believe the experience described by others is real, because it is not my experience.
What the 'left' is pushing is about gender roles.
A modern userstanding of gender has three parts:
Gender identity, which is you internal feeling of your gender (and most likely neurological/biological).
Gender roles - which is the social expectations placed on people based on culture - some cultures have had more than two gender roles in the past, including native american 'two-spirit' and Indian 'hiajra' (sp?) - but modern western culture has a strict male/ female dichotomy (this is socially constructed).
Gender expression - which is the only bit you really get a choice about, how do you express your gender, whether through clothes, behaviour, makeup, or anything else.
This is often a result a mixture if gender identity and gender roles.
It is only gender roles which the 'left' are advocating for abolishing - that is forcing men or women to do certain things segregrated by gender. Like only men being allowed join the army, or you could see the clergy as an all male social institution which the modern secularist would oppose...
By the way, deciding that you know better what other people are experiencing than they know themselves is rather insulting.