It takes a LOT of work and time to research these important topics. So, most of us tend to rely on information from groups that we tend to believe in general. Some groups are better at explaining and evaluating the information than others. Some [or most?] are promoting their own agenda, which may not be as obvious or 'transparent' as we'd like.
I [Willow] don't believe that all GMOs are 'bad' or harmful. I think there are many positive things about GMOs, and I also think that developing GMOs is not much different [usually] than the breeding practices that have been done for centuries on plants. Sure, there are things I may not agree with specifically about certain GMOs [for example, do I really want a plant that has a fish or pig gene in it? No], but in general, modifying plant genetics [which farmers and agricultural practitioners have been doing for centuries] generally leads to a better plant. [Note that Allan may not agree with me on some of these opinions.]
Anyway, I encourage you to do your own research, as well as take into account that if you lack a scientific background, much of the information may not be easy to understand.
One website I found that looks interesting and provides a place to start your investigation is called Vegan GMO, and the authors describe why the are pro-GMO. I encourage you to check them out and see what they have to say.
Also, here is a link to another video done by a vegan woman [Swayze] who describes several reasons why she is pro-GMO. Check 'em out and get your critical thinking caps on!