A very contentious issue, for sure!
Folks have made some good points. There is indeed a lot of mis-information out there--however, I am opposed to GEOs (Genetically Engineered Organisms)--their cultivation, marketing, consumption--all of it--for several reasons. I'll try to keep it simple and brief.
1. the patenting/ownership of seedstocks issue: Having a situation where a for-profit corporation owns a significant amount of the gene-pool that the populace relies on for food, and therefore survival, is a dangerous, stupid idea. It is not in the interest of the common good, period. This is pretty self-evident.
2. The excessive use of herbicides and pesticides, and chemical fertilizers: Most GE crops are designed to be used in conjunction with larger amounts of these than conventional crops. We already know these substances are all toxic (to people, animals, plants, and/or essential soil microbes) to greater or lesser degrees, depending on the specific chemical in question. They are also heavily dependent, for manufacture, distribution, and application, on fossil fuels. None of this is smart, especially given that better models exist (organic fertilizers, selective breeding, diversification, crop rotation, intercropping, green manure, sheet composting, grazing land in between cropping, etc).
3. Lack of comprehensive safety testing, etc.: the companies creating GEOs insist they are safe, but adequate testing
has not been done (or has been covered up and suppressed in cases where results suggested that the products might be harmful, we are told?) If testing has not been done, how can they know that they are safe? You see the problem here? If GEOs are indeed "safe," then it needs to be shown by rigorous, sincere, third-party testing, not somebody's word, or someone's hunch, or because the company trying to sell them says so. In fact, there is quite a lot of independent evidence that many of these food crops are NOT "safe." But even ignoring that, until better testing is done, I'm going to err on the side of caution and give benefit of doubt to the public interest groups and non-profits lobbying for consumer protection (and questioning the safety of GEOs)--not the companies presumably willing to cut corners to make a profit. Seems like the prudent course. If you want to buy a car, you don't just believe whatever the salesman tells you, you inspect things yourself or have a third party do it. The whole thing smells fishy no matter how you shake it.
4. Labeling and the right-to-know issue: Foods containing GEOs should be labelled as such, period. It's a simple issue of consumer sovereignty. Many consumers have made it clear they don't want GEOs in their food, and if consumers don't want them, they should not be hoodwinked into eating them. If processors are concerned that people will avoid the foods because they don't want to eat GMOs, then, oh well, that's that. Hey Monsanto--maybe you should have done more work to prove to us all that your products are safe before you introduced them! It's called the free market--people get to choose what they want to buy, whether corporations like it or not. And even if you or I think their choices are totally ignorant and wrong-headed.
IMHO, any one of these reasons is enough to discredit the whole GEO agenda. Taken together, it's way too much too swallow. "Feeding the world?" "Food security?" All of these ring hollow, and regardless just don't hold up when you look at the record so far. GEOs are about profits for seed/fertilizer/pesticide companies, not about advancing the common good. That's okay in and of itself, but they need to be demonstrated to be safe in every way, economically necessary, socially equitable, and generally beneficial, before they are allowed on the market--and so far they seem to be failing on all counts. The whole model is flawed.
Whether GEOs will actually give you or your chickens cancer outright or make you sprout a second head are debateable. Basic issues of human rights, consumer protection, and responsible business practices are not--at least they aren't supposed to be.
Well, that was neither simple nor brief, but there it is...