@galileogirl: I did pay attention in my social studies classes. You seem to be deliberately ignoring the premise of the question: everyone involved consents. Now, I could speculate about your reasons for this—principally, that you are nowhere near as tolerant as you claim to be, based on your slams directed at people who have a religious faith different than yours—but that would get us about as far as your speculations about how stupid the rest of us are, and how little attention we paid in school. Perhaps you are an aberration in the area you live, where everyone else reportedly respects the beliefs of others.
Consent makes the difference. In the case of your example 1: nothing prevents people who agree from donating a tithe to the church of their choice. Remember, since you seem to have a short attention span on this matter, that everyone consents and so there is no objection to this tithe—thus, it doesn’t need to be written into law. Making it compulsory is illegal, but remember, everyone consents, so it doesn’t need to be made compulsory by law.
In the case of your example 2: it’s illegal to use contractual language to place restrictions on who people can sell to, but there’s similarly no law to compel people to sell their property to people they do not want to sell to. Remember, short attention span woman: everyone consents. Again, making it compulsory to sell only to people of certain ethnicities or religions is illegal, but because everyone consents, there’s no need to make it compulsory.
I really wish you had paid attention to the requirements the government can not place on the behavior of private citizens. One of us was not paying attention in social studies classes, but it sure as heck wasn’t me.