The French government are perfectly entitled to pass the laws they want and enforce them.
Indeed, and everyone is perfectly entitled to express their opinions about the laws and consider if they would support or oppose them in their own country.
I do agree with your point that Westerners (male and female) are projecting their cultural mores when they attack the garb on the basis of how it demeans or oppresses women, but so what?
Shouldn't generally accepted cultural values inform our laws?
Immigrants move to a foreign land for personal advantage. This is perfectly fine, but it's unreasonable for them to believe that with their persons they can also transport all of the laws and customs of their native lands. Some degree of assimilation is always required even if it’s only something as prosaic as driving on the side of the road opposite of where they drive in their native land.
The French law, it seems to me, is intended less to empower Muslim women as it is to assimilate them into French culture. Not such a bad idea considering that a not insignificant number of Muslim imams in Europe promote the idea that the natives of their new homes should be assimilated into their
There is nothing wrong with immigrants wishing to preserve some sense of cultural identity, but apart from issues of personal freedom, there is a very real and legitimate incentive for the welcoming lands to ensure that if the newcomers plan on making their stay prolonged or permanent, that they, obviously, obey their laws but also adopt, in some measure, their cultural values.
I don't think any of us can say with any certainty that all or even most Muslim women secretly wish to see headscarves and veils outlawed, but I don't think this is a relevant consideration. Western women in Muslim nations wear headscarves in public, not because they have been converted to Islam, but because they're are guests of those nations and it is proper to respect the customs of one's host.
Muslim immigrants choose to live in Western nations and if they will not obey the laws of those nations or cannot abide their customs, they are free to leave and return to a homeland where the laws and customs are more to their liking.
Of course the situation becomes a bit more difficult when the welcoming nation grants citizenship to the immigrant. That the French law applies to native French citizens is not a persuasive argument of fairness when very few native French citizens would even think about wearing burkas. Perhaps these countries should have considered these issues before they granted citizenship, but they did not and should not now be prohibited from addressing them because they didn't exhibit incredible foresight in the past.
One can debate the magnitude of the threat of unassimilated Muslim immigrants, and whether measures like the French law are necessary, but I don't think it's realistic or reasonable to argue that creating such measures is improper.