With regards to patents:
Gene patents may claim the isolated natural sequences of genes, the use of a natural sequence for purposes such as diagnostic testing, or a natural sequence that has been altered by adding a promoter or other changes to make it more useful. In the United States, patents on genes have only been granted on isolated gene sequences with known functions, and these patents cannot be applied to the naturally occurring genes in humans or any other naturally occurring organism.
My other problem is that GMOs often are made for resistance to pesticides, and while that is great to ensure the harvest, the use of more and stronger pesticides is exactly what we shouldn't do, some pesticides are pretty harmless to humans, but those are not the ones GMOs are used to make crops tolerant against.
BT genes and RoundUp are both safe in the context of the average person's diet and safer for the environment than most other pesticides. Not that both don't encourage resistance, but that's a separate matter.
I'm not convinced either by regulation or that there is sufficient and qualified oversight or structure to safeguard against blunders that simply wouldn't be possible with normal breeding
Most previous generation plants didn't really fare well outside the environment of a farm (since their ancestors evolved to work well on a farm, not outside of it). Horizontal gene transfer / cross-pollination are indeed risks, but we're not really spraying RoundUp on forests. To be fair though, horizontal gene transfer always going on between species. And in the case of many GMOs, there are other environmental benefits that partially offset the risks.