Many religions support equal rights

many people are not religious and never will be

many people will never be one specific religion, like islam

Even the Menonites for instance, have started introducing womens rights, enforced by the laws, and their birth rate has gone down in some areas.

BUT

A non religious solution exists.

No voting, no property rights, that's it.

If society collapses from the population decline, their rights will be taken away anyways. This is a gentler solution for all.

Or invent mass scale cloning.