It's worth pointing out again that Sunday is not the Sabbath. Whilst Christian believers are free to regard one day more holy than another, and can set aside (for example) the Lord's Day or Easter Day or whatever as they choose, there is no Biblical basis for regarding Sunday as the Sabbath. This is probably a good thing, as the Old Testament law required God's people to stone Sabbath breakers.
Though I still would rather people believe in some sort of absolute beyond themselves, as these people do.
It is also worth pointing out that whilst Christians are not allowed to impose their values on other people, other people feel free to limit Christian freedom. Christians can't even look around in many places without being bombarded with materialistic, relativistic, blasphemous and sexual images that offend them but which are considered acceptable by non-Christian standards. Christians are certainly not allowed to suggest that their beliefs might be absolute, rather than relative.
It is also worth pointing out that if the Christian God really is there, and he made everything, then that God might reasonably expect a response from everybody - we are not actually free to choose to do what we want.