Woohoo! I'm popular!
Anyway, a couple thoughts on this. First, I don't honestly believe the people posting the anti-GMO/anti-Monsanto stuff are paid PR shills of the organic industry any more than I think that /u/JF_queeny and /u/adamwho are paid Monsanto PR. However, I would like to point out that the organic food industry (and yes, it is a multi billion dollar industry) has just as much reason to be doing anti-GMO propaganda as Monsanto (and Dow, and whoever else) have to be doing pro-GMO propaganda. Many of the anti-GMO accounts are just as single track focused on anti-GMO content as some of the pro-GMO accounts are focused on pro-GMO content. If you assume that one side is entirely corporate PR shills, than there is no reason to not assume the other side is full of corporate PR shills.
My thoughts on reddit's general pro-GMO trend: Back when this started to blow up again about a year ago, reddit tended to towards being anti-GMO as a whole. However, reddit is also generally pro-science (in a Rah! Rah! way, not in an overly meaningful way). After people started pushing back against the anti-GMO bad science (and there is a very large amount of it), reddit did have a bit of a shift. I believe there was also backlash as people started seeing that some of the anti-Monsanto talking points were factually incorrect (mostly having to do with their lawsuits). The fact that after the falsehoods were pointed out, the anti-GMO people kept hammering the same discredited talking points made them look bad to the general redditor. I think that this is what caused the sentiment to shift to be pro-GMO, which is why you see the pro-GMO posts get upvoted so much. A counter shift would require a similarly large event, which has not happened.
My personal thoughts: I am strongly pro-GMO technology. I think that Monsanto's R&D department is doing some really cool, cutting edge research. I think their legal department may be a little aggressive, but they aren't outside the norm for large heavily IP based companies, and are substantially less litigious than groups like the cellphone companies (Apple, etc), or the blatant patent trolls. I'm pretty neutral on their business department, because I don't really know much about them. I assume they are basically a large corporation, with all that entails.
The reason why I am active in some of the pro-GMO arguments is because I strongly feel that pseudoscience, wherever it is used, should be discredited. A lot of the anti-GMO arguments are grounded deep in the realm of pseudoscience, so I will go after those when I see them (though my personal pet area of pseudoscience that I care the most about is medical pseudoscience). I also dislike deliberate use of falsehoods in arguments (the Monsanto fairy is sneaking through fields, sprinkling seeds in its wake, and then summons its buddies the Monsanto Legal Ogres), so I will argue against those as well.
If you want to approach anti-Monsanto stuff from a stance that you don't think organic products or genes should be patentable, go for it (though I actually do see value in patents derived from research, so I might argue with you on that on). If you want to argue that Monsanto (and agribusiness in general) encourages monoculture farm, and that is a substantial risk, go for it. Just don't use deliberate, debunked falsehoods or pseudoscience.
Finally, I will say how much I appreciate how polite people are, even after I got linked here. The last time I was linked somewhere, I was hit by a pretty noticeable hostile brigade (that was by /r/shitstatistssay, who were upset that I believe government regulation of the pharmaceutical industry and doctors is a good thing).