Traditionally, the Islamic government legislates and enjoins these rules upon the people. Hijab is one of those rules. From our perspective there is no logical difference between this and Western dress codes in public.
The reason people find a problem with this whole Iran/Hijab thing is not because Women are being compelled to wear it. This wouldn't make sense because governments force things on us all the time.
The real reason is that they hate the hijab. To them, the hijab is oppressive, a sign of patriarchy, a sick form of sexual repression. I mean why else are women protesting in the streets because of it? Surely it must be a symbol of oppression that is finally finding expression in public? Right?
This is a much more sensible reason for us. The haters of Islam have always been running their mouths. They have never made a difference to us Muslims.