> This is a bit of a gray area because of religious freedom, but generally businesses open to the general public aren't allowed to discriminate against protected classes, because that used to go rather poorly for society.
It should not have to do with religion. It would be if it is a custom order; custom orders can potentially be anything. If they refuse a custom order, they can lose money and they can get a bad reputation, but that isn't to be disallowed, I think (unless they are going against what they have advertised).
They should not be allowed to refuse to serve black people, or white people, or gay people, or transgender people, or tall people, or bilingual people, etc, regardless of what is being ordered (including custom orders), and regardless of their personal opinions of such a thing; they should serve them anyways. (They may refuse to serve foreigners who do not have the correct money; if that is the case, then the customer will have to exchange their money elsewhere first, and then this business will be able to serve them.)
However, they may refuse to write certain words on the cake (regardless of what those words are, or what language they are written in), refuse to copy a complex diagram, refuse to bake a cake with a colour (or combination of colours) that they do not have, refuse to cast a spell on it, refuse to throw it at the wall, refuse to put a 3' cake into a 2' box, refuse to make something that you do not know how to make (especially if the customer refuses to explain), refuse to make something if the customer does not speak your language (and nobody is available who can translate; although if such customers are common then it would be good customer service to hire someone who does know their language), etc. If the customer is able and willing to alter the decorations themself when they get home, they can order a plain cake (or whatever parts they are willing) and then do the rest by themself at home.
However, refusing a custom order can give them a bad reputation and cause them to not earn the money from the sale that is not made; so it is better to accomodate reasonable custom orders if they can.
> If a business refuses to bake a cake for black people's weddings, is that okay?
I should think it depends on what exactly is ordered, like above. If black people come in and say they want to order a wedding cake, then it is not OK to refuse; they should bake a cake (and sell it to them, for the same price that they would charge anyone else) anyways. If they ask them to draw specific pictures on the game, then they might refuse (although it may give them a bad reputation, and they would not earn the money from the lost sale), although if the order is reasonable then it would be better to not refuse (regardless of their personal opinions).
> This sounds like a bit of an exaggeration of what's going on, but I think normalizing talking about sex would be a huge boon for education.
You are probably right; it is probably an exaggeration and that is what it seems to me, too. (I do not have any actual data or reports about this, though.) About the second part, that is a separate issue but also probably right.
> This one's iffier, I think it should come down to whatever the science says about what's a substantial advantage or not, ideally per-sport (and I'm sure some sports will have women with an advantage over men).
That is what I thought too. It will have to be considered individually for each kind of sports. It will also have to be considered why they have gender segregation, and if they should have gender segregation, and if so, what criteria they should use (it is not necessarily as simple as only yes and no).
And you are probably also right some will have women with an advantage over men (on average it will be; but this is not always the case between two specific individuals). (On average, men will usually have more physical strength, but women will usually have more physical endurance. This is what I had read in a scientific article about women hunting.) However, it is not necessarily only per sport; some are team sports with different designations of the people in each team; possibly women will have an advantage on average in some positions but not others, and tall people will have an advantage in some positions but not others, etc.
