Christians are not obligated to give up sex or “all early possessions”. At most they’re just obligated to give up personal trinkets during lent and fund the church. My point is that there is no coercion within Islam to wear a hijab, kinda like how there is no coercion within Christianity to be a virgin.
People who want to oppress women will do it regardless of means. Islam is just an excuse. There are many atheists who use their moral code instead.
To distinguish them, just get their confidence and ask them in a safe environment.