The danger lies in a patent owner seizing crops and/or suing a farmer out of existence.
But you probably don't believe there are people out there who want to control the world. What's the best way to control the world? Control the food supply.
I see no moral issue with a company protecting its intellectual property. Research is not cheap, and no one would be willing to invest the millions it takes to develop a new product if they did not have the legal protection of patents.
What's the best way to control the world? Control the food supply.
The food supply is not, and has never been, controlled by seed companies in a highly competitive market. Food supplies are controlled by politicians. Whenever you see people starving, look at the government: Venezuela, the USSR, China, any number of African despotic countries--the story is always the same. The politicians control the food distribution, and the people starve.
Furthermore, the fact that seed companies sell purposely non-propagatable seeds to large scale farmers does not prevent you from buying true-breeding "heirloom" seeds. There are seed companies that specialize in those, too. May I suggest Johnny's seeds?
I suggest you put down Organic Food weekly and read this article.