You're missing the point. I am not against GM foods for religious reasons. I am only against GM foods because they might affect my digestion in a negative way so if humans are genetically-altered and animals/plants aren't, that's fine with me. Now, granted, some genetically-modified humans might end up with severe health-problems as a result of faulty technology, here and there, but that's just natural selection at work. Those whose GM-techniques ended up in benefitting them more overall, would be the ones that survived. One thing's for sure, no "ordinary" human could possibly ever compete against a GM-ed human with a dozen extra senses, enhanced intelligence/strength etc. The ordinary humans would be destined for a life in the slums in perpetuity.
I'm not missing the point at all, I assumed that was your angle, though I'm not sure why you brought in religion, since that is not what has me against GM either.
But I guess I should back peddle a little bit. I have been against GE because it usually it involves putting some poison gene in to the plant that you're going to eat, OR it allows farmers to douse their fields (and my soil, water and air supply!!) with the worst kinds of poisons possible. But there is also my desire for purity, I don't want to be wondering whether some food I find growing in the woods is contaminated with modified genes. This can extend to us too, because microbes will be feeding on us, meaning that they will be eating GM foods. This is where empathy comes in.
I'm not saying someone can't willingly GE themselves, as I've said in the past, all things permissible to do, but that doesn't make them good or healthy. Also, it's not very nice to GM a new being without its permission, which is what your embryo scenario would entail.
If you want to GE yourself, great, I remember wanting more than anything to be a werewolf (with sentience and consciousness) when I was in elementary school. I remember vividly kneeling on the floor in the library area, reading a book about werewolves. I was super excited because there was a section labeled 'How to become a werewolf' but to my uber-religious (I was Mr. Baptist Fundamentalist Church Boy as a child) dismay, it claimed I had to make a pact with 'satan' for that to happen, there went my dreams of being a juvenile werewolf! And maybe yet today I would succumb to the temptation of retrofitting my genes to develop wings, or claws or flesh-tearing, bone crushing jaws. But then again, might not be worth the price (think frankenstein here)
The other reason is my lack of faith in technology. I see no benefit in antibiotics. I see no benefit in pharmaceuticals. No benefits in modern housing. Little to no benefits in any of modern medicine (not even physical trauma and surgery for the most part, see: Mutant Message Down Under). There is very little technology that I find truly useful in the grand scheme of things. The internet, yes, my smart phone, yes, media players, yes, transportation, yes.
But by and large, the ends put to our technology have not been beneficial. They have only enabled us to manhandle nature, pollute her and ourselves, cause countless extinctions of species and so much other sadness.