We know animal hormones increase animal weight but continue to assume they don't produce a similar effect in people? Are we intentionally being ignorant now about GM food?
The problem is that we just don't know because if we looked, we'd have to admit that maybe what we assumed was safe like we did with smoking in the 50's is really a killer. GM food might be safe but until it's proven, we should be very careful encouraging putting this into the environment.
To a liberal this makes sense but they're also the same people who continue to push material changes to society (read gay marriage) without the same rigor to understand it's long term impact.