Selective breeding performed slowly over longer time scales did at least give the breeders time to notice some kinds of severe problems. If you're breeding wheat and accidentally introduce a toxic mutation, you might notice the resulting pile of dead horses. There won't be a warning like this in every case, but it's not right to say that there's zero benefit to going slow.
That said, I don't really have an opinion on GMOs. I'm fine with you partaking first, though. :-)
That said, I don't really have an opinion on GMOs. I'm fine with you partaking first, though. :-)