I'm pretty sure that this worry is more about passing herbicide resistance to weeds, for example, canola and mustard are closely related, wild mustard can be viewed as a weed. This was the first result in a google search for "canola mustard hybrid". If, for example, they handle highway medians by spraying herbicide, and all of the sudden, the wild mustard can thrive in round-up, then they would have to use a more costly method for median maintenance.
That doesn't really seem like a big problem to me, not saying it's not a problem, but still it demonstrates it's possible. It seems at least to me that the potential benefits outweigh possible dangers and hassle.
My biggest objection to GMO's and the reason I strongly avoid them, is that I don't feel there has been enough research into the long term affects of eating them, ie what happens to a human who eats GMO corn three times a day for 50 years and I am not getting paid to participate in the study. If I was starving and GMO corn was the only thing to eat, then yeah I'm down, but I'm not, so I'll pass.
Here I suspect that you are being unreasonable, why would GMO in general be dangerous - any more dangerous than say some exotic fruit or what not? Yes you could - if you wanted - put a gene coding for a toxin into your crop, but if you just put in lets say a promoter for another already existing growth factor (up-regulating the gen). Why would that make you want you to avoid it? We haven't introduced anything new really.
I can see why road maintenance hassle doesn't outweigh potential benefits, but what about a gene for producing a pesticide. Resistance to herbicide doesn't present an obvious fitness benefit to a wild hybrid, but not being eaten by bugs certainly does. How would said pesticide affect bee populations if all the wild relatives of a given GMO crop now produced its own pesticide?
Admitting that I am at best a fledgling rationalist, I think its unreasonable to believe that GMOs are safe. Why does one believe that they are? Because researchers paid by or fun...
I was raised to believe that genetically-modified foods are unhealthy to eat and bad for the environment, and given a variety of reasons for this, some of which I now recognize as blatantly false (e.g., human genetic code is isomorphic to fundamental physical law), and a few of which still seem sort of plausible.
Because of this history, I need to anchor my credence heavily downward from my sense of plausibility.
The major reasons I see to believe that GMOs are safe are:
The major reason I see to believe that GMOs are dangerous is:
So: green goo, yes or no?