An an ad agency, corporation, non-profit, or politician is not allowed to do the following or hire someone to do them:

• Build or commission others to build, a Minecraft mod, map or server that promotes or markets unrelated products or services in playable form; for example, you are NOT allowed to market or promote a branded automobile using a mod that depicts branded automobiles within Minecraft game play;
• Build or commission others to build, a Minecraft mod/map/server that promotes or markets a company’s movie or TV show; for example, you are NOT allowed to build maps and/or videos using Minecraft blocks that build out the world or characters of a movie to promote and market your company’s or your client’s movie or TV program;
• Offer Minecraft gameplay displayed or projected publicly within physical locations; for example, you are NOT allowed to promote or advertise big-screen Minecraft gameplay inside restaurants or other commercial venues; and you are NOT allowed to charge money for Minecraft gameplay, leagues, or competitions in theaters where gameplay is projected onto the movie screen;
• Create or commission others to create promotional or marketing videos or movie trailers through Minecraft gameplay; for example, you are NOT allowed to create or produce movie trailers through Minecraft gameplay for promoting or marketing a movie;
• To promote your (or your client’s) corporate brands, products, or services.

However, certain actions are allowed:

• Pay to advertise your business in an advertisement window within a Minecraft video; for example, by displaying a banner ad or by selling your ads on YouTube where they may be shown in connection with Minecraft videos uploaded independently by players;
• Pay for advertisements of your business to be served on websites or servers related to Minecraft, so long as you are not hiring the server operator to design or host a Minecraft mod/map/server that builds an in-world representation of your brand, products, or services.
• Build products or movie environments that you are a fan of into a Minecraft mod/map/server so long as you have not been asked to do so by the entity who makes the product or by someone they have hired to promote their brand or products; likewise, you can express your support for a political candidate in a map/mod/server, but not if you have been hired to promote them.

I really don't understand this at all, it seems completely ludicrous to me.

Why shouldn't a company or a person working at that company be able to make a minecraft world/server based on their IP. Minecraft servers are privately hosted on people's own computers, it has nothing to do with Mojang.

If Ford want to make a minecraft mod that adds their cars to the game and release it for free why shouldn't they be able to?

If Nintendo want to recreate the Kanto Region from pokemon in Minecraft, why shouldn't they be able to?

It's not like Mojang is hosting this content, it's hosted on computer/server hardware owned or paid for by the server owner. People making content for your game and releasing it for free should not be hindered like this, it's ridiculous.

If  companies were paying people to go onto random online servers and put up advertisements for their products that's one thing, if companies want to host their own server or release minecraft worlds based on their IP's or products that's another thing entirely.

There's no reason to ban companies from creating Servers, Worlds or Mods based on Franchises, and I'm unsure how Mojang even have the legal right to this, they don't host the servers and it's a sandbox game how can you tell people what they can and can't build?

This move can only be harmful to the game, it's stupid.