Secularism isn't a deen and doesn't impose religion on anyone but doesn't just allow people to freely choose to practice a faith it protects that right legally, it also separates religion from government rule, it sees them as two distinct sectors of society.

In my opinion the state has no business telling people what to wear, it's authoritarian and leads to resentment.

What they are trying to say is that no matter what a society decides for it's standard of dress, that standard must be based on a set of beliefs. What you have done, and i see a lot of people making this mistake today, is place Islam in the category of 'religion' but consider the secular liberal worldview as some kind of default neutral position. So it's not considered a matter of 'force' with the standard of dress a secular country like America imposes on them today, but if a country decided to base it on a Divine book, suddenly it's considered "forceful" and "oppressive". When in reality all laws in modern nation-states are based on a set of beliefs and they are all 'enforced' on the public. If there really was a default neutral position, it would be having no laws at all, no standard of dress, nothing. But this doesn't happen the civilized world.